2008 Chevrolet Silverado, Cruise Control Does Not Work, P0573

This 2008 Chevrolet Silverado came in with the complaint that the cruise control would not work. Since I have a Tech 2 scan tool I decided to look for codes first. There was a PCM code P0573 stored for the “Brake Switch Circuit 1 High Voltage”. Simply put the computers think that the brake lights are on and the cruise control is disengaged.

The test is to look for power on the light blue/white wire at the stoplight switch. The key must be on and you will want to check for power on that wire with the brake pedal released and also gently pushed.

What was happening on this one was that the cruise would engage and later it would turn off because of a very sensitive switch and rough roads. An easy test is to drive the vehicle until the cruise turns off. Note the roughness of the road. Driving under the same conditions and of course with no other traffic around, place your left foot under the brake pedal and gently lift up. Try the cruise again. If it continues to work depress the brake pedal to disengage the cruise control. It should be noted that a problem with a towed vehicle wiring can result in a similar condition with the cruise control.

I knew I needed to get to the stoplight switch and removing the lower duct work would make that easier.

There is a push pin retainer that holds the outer end in place. Once it is removed the duct can be slid out of the vehicle.

The stoplight switch is shown slightly above center in the following picture.

There is a bolt with a 10 mm head that needs to be backed off or removed so that the reatining clip can be removed.

The latch that holds the harness to the switch has to be depressed before the harness connector can be removed.

A few closer looks at the switch retainer with bolt.

The switch strangely enough looks quite a bit like the old Ford stoplight switches.

This vehicle had adjustable foot pedals and the view would be slightly different if the pedals were of the fixed type.

Although this is termed as a BPP (Brake Pedal Position) switch within GM Service Information no setup or programming is needed when replacing this switch.

If the code had been P0572, testing would have started at the Misc IGN fuse in the underhood fuse box. It would be in position #43 with a gas engine and position #40 with a diesel engine. This fuse sends power to the stoplight switch on the pink wire.

2002 Lexus RX300, Passenger Low Beam Headlight Does Not Work

This 2002 Lexus RX300 came in with the complaint that the passenger side low beam headlight and the driver’s side driving/fog light did not work.

I located the fuse in the under hood fuse box.

Testing showed that the fuse was good and properly powered.

To access the wiring for the passenger side low beam headlight, I found it easier with the windshield washer reservoir fill tube removed. One bolt with a 10 mm head holds the fill tube in place.

With the bolt removed the fill tube will pull up and can be removed from the vehicle.

Now there is easy access to the low beam headlight bulb harness connector.

There is a thumb latch that has to be depressed to release the connector. The picture below is a little deceptive. Where my thumb is located is not where you would push down. Instead you would want to depress the end that is closer the the actual wires.

I check for power at both terminals and none was present. I went to the wiring diagrams to make sure that there was nothing except wiring in between the fuse and the headlight harness connector. There was not. The customer had stated the she had just gotten the vehicle back from the body shop where it had been for some front end damage. My assumption was that there was a broken wire. A closer look at the wiring diagrams revealed the answer and it was further confirmed with a visual inspection of the car. The diagram indicated that the red wire with a blue stripe was the power supply wire for the headlight bulb. The connector that I had been checking had a red wire but it had a black stripe. Also notice that the connector body is gray in color.

Looking over at the connector on the driver’s side low beam, I saw that the body color was brown.

Further inspection of the wiring for the passenger side headlight assembly found that there was a brown connector fastened to the lower bulb.

As it turns out the low beam headlight bulb and the driving/fog light both use the same bulb and therefore the same harness connector. Notice that the brown connector has a red/blue wire and the gray connector has a red/black wire.

Now the harnesses are properly connected to the appropriate bulb. If you look closely at the lamp assembly, there are color codes rings around the two bulbs to indicate which connector fits.

Now both low beams work at the same time.

I had to point this switch out to the customer. The inner ring that I am holding is the driving/fog light switch.

Now you can see that all lights work as they should.  What initially seemed to be a complicated issue was just a simple fix. Had some one noted the color coded rings and harness connectors during reassembly, the problem never would have occurred.

Oh well, another one fixed. 

2002 Chevrolet Tahoe, Dash Lights Do Not Work

This 2002 Chevrolet Tahoe came in with the complaint that the dash illumination lights would not come on. These lights are sometimes referred to as panel lights. Testing begins at the illumination fuse in the interior fuse box. The fuse box is located behind this panel on the driver’s end of the dash.

With the park light switch on and the panel dimmer switch in the bright position there should be power at this fuse. There was none.

I did find that power would appear when the panel dimming switch was raised up above the detent to turn on the dome light. I looked over and the panel lights were on.

The next step in testing would be to remove the headlight switch. The panel dimming switch is part of the headlight switch assembly. The instrument cluster facia pulls loose from the dash carrier. The steering column needs to be placed in the full tilt down position. The shift lever needs to be pulled down into the lowest gear position also. When removing this panel the top edge will have to be tilted out first. You will find that the inner edge over the instrument cluster will not come fee easily. You will need to carefully bow down the inner edge so that it will clear the dash carrier. Use just enough force to clear and no so much as to break anything. Ninety nine percent of the time the hazard flashers will be turned on during this part of the operation. The alternative would be to drop the column but I have never needed to.

There are retaining clips at the top left and lower right edges of the headlight switch assembly. Once released the switch will pull out of the dash.

I checked the dark green wire (terminal K) at the rear of the switch assembly for power under the same conditions as when I tested the illumination fuse circuit. This wire supplies power to the illumination fuse. Power is routed to terminal “K” internally from terminal “B” (orange wire) of the headlight switch. Terminal “B” also routes power through the headlight switch for the exterior and interior park lights. Since I could visually see that they worked, I did not have to test that part of the circuit. That signal is sent out on the light blue wire terminal “A” of the headlight switch connector.

The same  circuit test with the panel dimming switch rolled past the detent.

The same wire with a new switch installed and the switch positioned about half way.

With the switch rolled almost off.

The panel lights now work as designed.

While I do my best to detail as much information as possible. There are many repairs that I have yet to document and some of you may wish to have more than I have provided. I would strongly recommend subscribing to one or both of the following data companies for further assistance. Although having an abundance of information does not guarantee an easy repair, the lack of adequate information will guarantee a failed repair!

Need more information? Subscribe to Mitchell1 today!

Do it Yourself Automobile Repair Information

2007 Pontiac G6, Changing The Headlight Bulb & Harness Connector

This 2007 Pontiac G6 came in with the complaint that the passenger side low beam headlight had stopped working. The vehicle’s owner stated the the light would come back on sometimes if she hit a bump in the road. That condition would indicate a poor connection and more than likely it would be at the bulb itself.
To remove the headlight assembly the fasteners that hold the top center of the front bumper cover in place have to be removed. The center portion has to be lifted up. This can be done with a small screwdriver. Two makes it easier.

Once the center pin is lifted far enough as shown below.

The whole pin can be pulled from the body panel.

Now the two screws that hold the light assembly in place can be removed. The screws have 7 mm heads.

The light assembly has to be lifted enough to clear the bumper cover and at the same time the outer corner has to be pulled away from the fender.

It takes some maneuvering around to free the assembly.

Once free of the vehicle the assembly has to be flipped over to gain access to the harness connector. First the thumb latch has to be lifted slightly.

Then the connector bodies can be separated as shown below.

Now that the assembly is on the bench the cover over the low beam headlight bulb can be removed.

It turns to the left and can be a little stubborn.

Once the cover is removed the bulb and socket can also be rotated to the left to free the bulb from the housing. As suspected the bulb and harness connector have heat damage and both need to be replaced.

If you need one of these harness connectors please click here.

When splicing in the new harness connector this trick works well. There are two black wires that originally were crimped into one of the terminals in the socket. The new socket comes pre wired and only has one wire on each side. Join the original two wires together with a splicing terminal. Strip enough insulation from the wire from the new connector so that the bare wire can be folded in half. That will double the size of the wire on the new connector so that it will properly mate with the splice terminal that was used to join the two black wires together. Of course the heat shrink tubing needs to be installed on to the wiring before joining all three wires together.

The new bulb and harness connector installed into the light assembly.

Another one done.

2004 Jeep Grand Cherokee , Code P0122 Set, Runs Poorly Sometimes

This 2004 Jeep Grand Cherokee came in with the complaint that the engine would buck and jerk and sometimes stall. There was a code P0122 stored and the TPS had already been replaced in an attempt to repair this vehicle. The customer stated that the oxygen sensors and the crank position sensors had also been replaced due to codes being set for them as well.  I did a little investigating and found a problem with the wiring harness at the rear of the engine slightly to the driver’s side of the vehicle. If you look at the wiring harness at the rear of the engine in the next picture you should be able to see that it may be resting on a stud extension on the last head bolt.

If you enlarge the next picture and look in the mirror reflection you can get a slightly better view.  Lifting the harness and securing it away from the stud could be enough to alleviate the concern temporarily.

To fix it, a little more work is needed.  I actually did not find the problem until I did some testing at the TPS. At the TPS connector the orange/red wire is the signal wire to the PCM from the TPS The orange wire is the five volt reference from the PCM to the TPS and the black/lt blue wire is the sensor ground. Looking at the data on my scan tool showed a TPS voltage of zero volts. I jumpered the five volt reference wire to the TPS signal wire. The scan data voltage should have gone up to five volts but instead remained at zero. The diagnosis would have to be either the TPS signal wire shorted to ground or a faulty PCM. Following the wires around and lifting the harness, in the previously mention suspect location, caused the TPS data voltage to increase to 5 volts. Diagnosis shorted TPS signal wire.

The plastic housing that mounts on top of the throttle body assembly needed to be removed so that I could easily access the TPS connector and wiring. It also needed to be out of the way for repairing the wiring harness.

There were several mounting screws and hoses that had to be detached  from the housing.

The only one that is slightly tricky is the one for the rubber boot that sealed between the housing and the throttle body bore.  The clamps for the air intake tube also need to be loosened so that connection point can be disassembled.

A view of the same screw from the underside.  Even with loosening the clamp the boot may stay on the throttle body or the housing.

To get enough room to work comfortably, I also moved the hoses and cables shown in the pictures out of the way. I had to carefully cut the old split loom and tape off of the wiring harness. I lifted the harness shield that runs the length of the engine off of the head bolt studs. This allowed me to maneuver the harness around enough to work on it without having to fully remove it.

I had to cut a short section out of the orange/red wire.

I repeated the repair on a second wire that I found damaged also.  I used heat shrink tubing to seal and protect the splice joints.

This is the damage on the underside of the original split loom. A combination of heat and vibration against the stud over several years is what damaged the loom.

I cut a new piece of split loom to length.

Installed the loom and re wrapped with tape.

I cut a short piece of rubber hose to use as a protector over the stud.

It will probably never happen, but if the harness works it’s way back down again the rubber hose will keep the wires from shorting out on the steel stud.

Except for installing the breather housing back onto the throttle body this one is done.  Notice that the rubber sealing boot is on the throttle body. I took it off and installed it back onto the plastic housing before the final assemble.

2008 Mercury Grand Marquis, A/C Stuck On Heat

This 2008 Mercury Grand Marquis came in with the complaint that the a/c temperature was stuck on full heat. The complaint could have easily been reversed with no heat present and the system stuck on full cold. It has Automatic Temperature Control (ATC). I used my scan tool and found that there was a code B1249 stored for a fault with the blend door actuator.

This repair will be very similar if not exactly the same for a Ford Crown Victoria or Lincoln Town Car of the same era. There are ways to check the system without a scan tool but some disassembly is needed. Starting at the passenger side of the dash, the center trim panel has to be pulled free of the dash carrier. It is held in place by spring clips.  On this one some extra effort and care was needed for the clips below the HVAC control head. There are also several switch harnesses that have to be disconnected so the trim panel can be placed out of the way.

Next, there are four screws with 7 mm heads that have to be removed to pull the HVAC control head from the dash.

The two motor controls wires need to be back probed and the leads attached to a multimeter set to DC volts. The wire colors are violet and brown/green. There are two wires of each color in this connector and I strongly recommend you obtain a wiring diagram to insure that you are on the correct wires. You may be able to tell by clicking on and enlarging the next picture. The violet wire is in the far left slot in the forward row as shown in the picture below. The brown/green wire should be in the second row, two slots from the far left. It will have an orange/black wire to it’s left side and an empty slot to it’s right.

There should be a nominal 12 volt reading across the two wires as the motor is commanded to move. The polarity will shift as the direction of travel is changed. A few things to keep in mind are that if a hard code is set, this signal may be missing or if the actuator motor is shorted the readings could be substantially lower. You may need to disconnect the harnesses from the HVAC control head assembly for a couple of minutes to clear the codes. You may also have to disconnect the harness connector from the actuator or both.

To test the position feedback circuit of the actuator you must back probe the yellow/green wire in the gray harness connector with all connectors fastened. It is in the forward row and third from the left. A nominal 4.5 volts indicates the full heat position.

While a nominal .5 or 1/2 volt indicates the full cold position. These test results were gotten after the new actuator was installed.

To gain access to the actuator the glove box needs to be removed. There are two 7 mm headed screws located in triangle slots at the glove box hinge. Then the box can be opened and removed from the dash. There are two stop pegs on either side that have to be maneuvered around to freed from the dash opening. With the glove box removed you can look up and to the left of the opening and locate the blend air door actuator on top of the HVAC box. You should also be able to disconnect the harness connector if needed for testing. It takes some finger tip coordination.

Unless your arms are skinny and you are very coordinated , some other parts will need to be removed to replace the actuator. Keep in mind the proper procedure involves dropping the column, removing the dash assembly and loosening the HVAC box. It is a 5.4 hour job if you have experience doing it. What I am going to show you is how it can be done with minimal disassembly in 1.5 hours or less. It does require having a good tool inventory, long fingers and good fingertip coordination.

The passenger side air bag will need to be removed and please follow the manufacturers instructions on how to do this safely. After disarming the system there are two 8 mm headed screws on the underside that have to be removed.

There are two 7 mm headed screws along the lower face of the passenger side air bag assembly.

There is one screw along the lower edge of the far right vent that has to be removed before the vent assembly can be removed.

The vent duct work needs to be removed. There are two screws that hold the duct to the inside of the dash carrier. They both have 7 mm heads.  For some reason the upper one has a zinc chromate finish (yellowish). I guess that was an easy way to distinguish it from the others  since the type of threads are specific to fastening into plastic materials.

The lower one has a black finish and is the same type of threads as the rest of the 7 mm headed screws removed to this point.

Perhaps the most physically difficult part of this job is removing and installing this piece of duct work. I was able to force the duct far enough to the right to be able to slide the left side forward and off of the main trunk. When reinstalling it I had to use a plastic pry bar and multiple screwdrivers to  get the duct in the proper position and then work the outer edges free so that it would slide back over the main duct work trunk. Luckily the plastic on the left edge is reasonably flexible and recovered it’s original shape.

The white flex hose is clipped into the left underside of the above duct. This picture was actually taken during reassembly but you should be able to get the idea.

It took a good bit of effort but the duct was finally free of the dash.

Now there is a lot more room to see and work. One of the front screws is easy to see but the rear screw needs a mirror to get a clear perspective of it’s location.

In the next picture I am showing the tool and the technique for removing the rear screw. Obviously the actuator is removed to give you a clearer picture of the procedure.

This is how it would look with the actuator in place. Even with this tool I was not able to fully remove the screw. I had to finish removing it with a pair of long curved jaw needle nose pliers. Some people advocate simply breaking the actuator at that screw location and then removing the debris and loosening the screw. I had good tools and did not want to take the chance of the wrong plastic pieces breaking.  If you attempt breaking that corner of the actuator, it must be done with the other two mounting a screws removed. Some earlier year models may have a total of four screws. By the way they all have 8 mm heads.

The most physically challenging screw to remove and install (installing is the harder of the two) is the one that is 3.5 inches to the left of the visible forward screw.  Installing the screw required me to use my left hand through the opening behind the radio and my right hand through the glove box opening. I have large hands but you can see in the picture below there is some physical discomfort involved in this job. I also had to use a curved body tool with a piece of vacuum hose attached in my left hand to hold my ratchet and socket in place on the screw head as I used my right hand to work the ratchet.

The squared corner of the duct work is what  makes it difficult. On the next car I may consider cutting it off and sealing whatever hole is left.

In the next picture you can see the white harness connector for the actuator.

Before installing the new actuator I cut a slot for the rear screw. This allowed me to have the screw installed but loose so that the slot would slide around the threaded part of the screw. Once the actuator was properly positioned all of the screws could be tightened down.

Below is an accounting of all of the tools that I used to do this job. Some are very specialized and many mechanics will not have them so it is highly doubtful that most DIYer will have them either.

The old actuator on the left and the new one on the right. Notice that I have not cut the slot for the one screw yet.

1994 Honda Accord Tip In Acceleration & Stalling Problems When Warm

This 1994 Honda Accord came in with the complaints that the engine would develop a bad tip in acceleration problem as the engine warmed up. Also after the engine was warmed up and the throttle was opened once the idle would become very erratic and the engine would stall if the throttle plate was not kept open and continually feathered. I tried reading codes while the condition was present and could not establish communication between the scan tool and the PCM.

I also tried reading codes by installing a jumper wire in the two wire diagnostic plug under the passenger side of the dash.

The diagnostic charts were a little unclear about how the light should react if there were no codes. In my case the light would come on but it would not flash. I thought at the time it was significant but after fixing the problem and making sure there were no codes with the scan tool the light still would not flash, on steady when the diagnostic connector was jumped.

In testing for a system that will not enter diagnostics I found a test that involved disconnecting three different  engine sensors.  The first on was the MAP sensor. Disconnecting it did not re establish communications.

Next up was the TPS. Same reaction as above.

The last sensor was the ERG position or lift sensor. Disconnecting this sensor did re establish communications between the scan tool and the PCM. It did not make any difference in how the engine ran though.

It seemed unlikely that an EGR position sensor would go bad under the warm up conditions and then heal itself after a long cool down. What if the EGR valve was going full open after warm up. Disconnecting the vacuum hose at the EGR valve produced a distinctive pop of the EGR valve closing. I started the engine and it ran normally. While the engine was running, I reconnected the vacuum hose to the EGR valve and the engine continued to run normally. Opening the throttle induced the tip in acceleration problem and subsequent stalling condition.

I traced the vacuum hose back to it’s source and all appeared to be okay.  I disconnected the harness to the EGR valve control solenoids and the problem went away. Reconnecting it and raising the engine rpm’s would bring the problem right back.

I then took a really close look at the two hoses that come from the engine and the EGR valve and eventually connect to the EGR control solenoids.  The hose connecting to the EGR valve is labeled #16. The hose connecting to the intake fitting was marked #24.

I followed the #24 hose from the intake port along the metal tube to where it reconnected to a rubber vacuum hose that was labeled #16. You have got to be kidding me the problem is that simple.

The hoses looked as if they were properly positioned and has a smooth flow from the engine to the connection points on the strut tower. However they were crossed. The #16 hose belongs on the upper pipe and the #24 hose connects to the lower pipe.

The above picture has to hoses connected incorrectly. The picture below shows the correct hose connections.

A couple more pictures of the hoses and how the connect and are routed.

The really sad thing about this car is that the engine was changed in an attempt to correct the problem. Along with the distributor and the PCM. It did have some very real problems with the coolant temperature sensor, spark plugs, spark plug wires and distributor rotor. All of that had to be corrected before the engine would run well enough to get to this diagnosis.

In case you wanted to know what was actually happening, by design the EGR valve is controlled by the PCM. The engine has to be up to operating temperature before the PCM will command the EGR valve to be opened. It is also varied according the engine rpm. With the hoses crossed the EGR valve was being commanded to open but the system could not properly vent the vacuum to release the EGR valve and allow it to close again. The more the throttle was opened the further the EGR valve was opened and a large internal vacuum leak was created. This caused the tip in acceleration problem and the resulting stalling condition.

While I do my best to detail as much information as possible. There are many repairs that I have yet to document and some of you may wish to have more than I have provided. I would strongly recommend subscribing to one or both of the following data companies for further assistance. Although having an abundance of information does not guarantee an easy repair, the lack of adequate information will guarantee a failed repair!

Need more information? Subscribe to Mitchell1 today!

Do it Yourself Automobile Repair Information

1995 Chevrolet S10 Pickup, Rear Lights Go Out

This 1995 Chevrolet S10 pickup came in with the complaint that the park lights would work until the brakes were applied or the turn signals were switched on. In reality none of the rear lights were working as they should. It all sounded like a bad ground to me so I wanted to start by checking the ground at one of the bulbs.  There are two phillips headed screws that hold the light assembly in place. Once removed the assembly will pull out.

The socket twists to unlock and then pulls out of the lamp assembly.  Note the bulb elements in the following picture. Although only the park/tail lights are turned on both elements are glowing and neither one is bright. This is due to a poor ground condition.

To further prove the faulty ground condition I back probed the black ground wire where it enters the socket assembly. Note that my test light is illuminated in the next picture. This is due to un grounded  power back feeding the ground wire.

This was a pretty easy diagnosis when I spotted the cut ground wire under the driver’s side rear of the truck.

The factory ground bolt was heavily rusted and would not come loose without a lot of effort. It is just barely visible at the center of the next picture.

Instead I drilled a new hole in the frame.

I lengthened the damaged wire and added a ring terminal. I secured it to the frame rail with a self tapping screw. It does not look like it but I did wire brush down to clean metal.  Afterwards I sprayed some black paint on the connection point.

Now the stoplight  element is bright when the brakes are applied.

This customer is going to have a lot more problems with this truck due to heavy rust on the underbody.

2003 Ford F150, Odometer Works Sometimes

This 2003 Ford F150 came in with the complaint that the odometer works sometimes and sometimes it does not. The customer stated that it rarely works now. As you can see in the next picture it was not working when it came in. I have done a few of these in the past and have been waiting for an opportunity to do this post. The problem is weak solder joints inside the instrument cluster assembly.

The first step in removing the instrument cluster is to remove the upper steering column trim panel. The panel is snapped into position and is relatively easy to remove. Start at the lower right side and work you way up and around to the left of the steering column. Once the panel is loose, switch the ignition on and move the gear selector down. You may also want to tilt the column down.

There are three screws along the upper edge of the instrument cluster trim panel that have to be removed. They all have 7 mm heads.

There are two screws, one at either side of the instrument cluster. They are on the outer edges.

The headlight switch has to be pried out of the dash. Be careful to protect the dash surfaces as they are easily damaged/scuffed. I used tape along the lower edge where the initial pry point is located (slight notch). Make sure that you use a tape that will release without damaging painted surfaces. Especially if the dash has been cleaned (Amour Alled). I also wrapped the tip of my screwdriver with tape so that the finish would bot be damaged as I worked my way around the headlight switch bezel. In some cases it may be better to just wrap the screwdriver tip.  In earlier model trucks you had to go through a series of motions to actually unlock the switch from the dash. Prying those switches would result in damage to the switch and the inner dash retainers.

There is one screw behind the headlight switch assembly.

Now the ignition can be turned on, the steering column tilted down and the gear shifter can be pulled down into low range. The brake pedal will have to be depressed to move the shifter.

There are four screws located at the corners of the instrument cluster that have to be removed.

The instrument cluster can now be lifted and tilted slightly so that the clips that hold the gear shift indicator in place can be depressed and the shift indicator can be gently removed. It is tedious and delicate work.  Sometimes I just remove the steering column covers and disconnect the other end. Depends on my mood and what I think my chances are of breaking anything are.

Tilting the instrument cluster some more will now allow you to reach behind the cluster and disconnect the two wiring harness connectors. Some year models have more connectors. There are thumb latches that have to be depressed before removal.

With the cluster removed, I had to turn it face down on a piece of cloth to protect the lens. Then the screws (5.5 mm heads) all around the outer edges had to be removed. The back cover lifts off.

The ribbon cable had to be carefully removed. Prying out on the latches while pulling up on the connector body. Do not pull on the ribbon cable itself.

The circuit board has to be carefully lifted off of the remaining instrument cluster assembly. There will be resistance at the points where the gauge pins are inserted into the mating sockets that are part of the circuit board.

Make sure that the gray silicone contact part of the trip odometer reset button stays in place.

Now that the circuit board is fee of the remaining instrument cluster the faulty solder joints will need to be located and repaired. They are on the underside of the ribbon cable connection point.

If you have good eyes you may be bale to spot the cracked joints. They are normally located at either end of the connector.

If you will click on and enlarge the following pictures you should be able to see the black rings around the solder joints.

The rings are the actual separation points. I resolder all of the joints of this connector while I am there.

Gently and evenly push the circuit board back onto the instrument cluster assembly. The push the ribbon cable back onto the circuit board connector. It takes a little bit of effort to seat the connector. Put the cover back on, connect to the dash wiring and test the repair.

Success.

I should point out that before installing the cluster that I removed the lens assembly (being careful to not leave finger prints that will collect dust). I then used a fine brush to remove as much dust as possible.

Of course I had to reassemble everything. Installing the shift indicator assembly back into the lower edge of the cluster is probably the most tedious and difficult part of this repair.

Another one done.

2003 Chevrolet Silverado, HVAC Actuator Stuck

This 2003 Chevrolet Silverado came in with the complaint that the passenger vents were stuck on heat at the end of August in South Carolina.. Since it was late I decided to try a procedure that GM came out with several years ago. It applies to actuators that have over traveled for one reason or another. The following is an excerpt from the GM bulletin.

“Concern/Condition:

A replacement HVAC actuator is inoperative or has worked one time and quit.

The HVAC control head learns the stopping points based on how far the HVAC DOOR travels. If it reaches the mechanical stops on the back of the actuator, it will be outside the range that the HVAC control head can learn. If the actuator was not mounted to the HVAC case prior to plugging in it’s connector, the actuator will go out of range and will be inoperative.

Recommendation/Instructions:

Always attach the HVAC actuator to the case before installing the electrical connector.

If an actuator is out of range, it may be possible to bring it back into range by following the procedure below:

  1. Turn ON the ignition with the engine OFF.
  2. Connect a 3 amp fused jumper wire between the actuator control circuit and the 5 volt reference circuit of the actuator connector.
  3. Remove the jumper wire and actuator connector when the actuator is at the center position.
  4. If the actuator doesn’t move in step 2, try installing the jumper wire from control circuit and the ground circuit of the actuator.
  5. With the actuator in the center position, install the actuator to the HVAC case and secure the mounting screws and then connect the actuator connector.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.”

The above information seems to have been provided by GM mainly to combat actuators being stuck when the harness is connected and the actuator is not attached to the HVAC box and thus being returned as defective. That is all fine and dandy but we can use this information to un stick and actuator that has over traveled due to other causes. Mainly, there has been a problem with over travel caused by compression of the foam sealing layer on the actuator doors themselves coupled with loose software parameters that did not originally take this into consideration.  Also we can use this information to add to diagnostic routine that may not include the use of a scan tool capable of interacting with the HVAC system.

The first thing that I had to do was to make a workable fused jumper wire with a 3 amp fuse.  The next picture is what I came up with. I used a set of multimeter leads and a fused jumper wire together. The multimeter leads gave me the contact point that I needed, which was a solid piece (no frayed wire ends that could possibly bridge multiple circuits) and  that was long enough to back probe the junction block harness in a comfortable manner.

I used an ATO style fused jumper wire. Made from an inline fuse holder.

I had attached small blade terminals to the in line fuse holder to make it a fused jumper wire. I inserted the blade terminal into the cross pattern in the meter end of the test leads. Together I have a very functional fuses jumper wire.

Now, the test point. The most practical point to do this test and more is at the passenger side junction block that is located under the cover located at (you guessed it) the passenger side of the dash.

I backprobed  the white/black wire slot of the C8 connector, pin E with one lead of my 3 amp fused jumper wire. The C8 Conneector is the gray upper middle connector as shown in the next picture. Please click on the following pictures to enlarge them for a better view.

Pin designations of the C8 connector as viewed from the wire side of the connector.

“A”     White/Black, Lower left corner, Lower left air duct temperature sensor with auto controls.

“B”     Brown (2), Left  side middle, Ignition “3” voltage  for the left & right air temperature actuators.

“C”     Brown (2), Left upper corner, Ignition “3” voltage for the mode
& recirculation actuators.

“D”     Dark Blue, Upper Right Corner, Passenger side air temperature door
POSITION signal with auto controls.

“E”      White/Black, Right Side Middle, Passenger side air temperature door CONTROL signal with auto controls.

“F”      Dark Green, Lower Right Corner, Recirculation door CONTROL signal.

With the other end of my 3 amp fused jumper wire, I backprobed the light blue/black wire of the C4 connector pin “H” for one direction of travel. For the opposite direction of travel I  connected to the “M” pin. Sorry at this point I do not remember which one moved a particular direction. The C4 connector is the large brown connector in the upper left corner of the junction block as seen in the next picture. Please click on the picture to enlarge for a better view. It did free the stuck actuator and I was able to disconnect the actuator harness to prevent anymore unwanted heat. The vehicle will still need an new actuator as the old one is actually faulty. Although I used a Tech2 scan tool to determine the actuator was faulty, the same can be done by monitoring the voltages on the command (control signal) and the actual position (position signal) of the affected actuator. We would be looking for a smooth voltage change on the position signal as the actuator is commanded to move. It should range from a nominal 0 volts to a nominal 5 volts. The range will be smaller than this but I am trying to get this post completed and will update it later with more specifics. The command or control signal should be either 0, 2.5 or 5 volts. 0 volts is a command to travel on one direction. 2.5 volts is a stop command. 5 volts is a command to travel in the opposite direction of 0 volts.

Pin designations of the C4 connector as viewed from the wire side of the connector.

“A”     Black, Lower left corner, Ground

“B”     Gray/Black, Left side middle, Lower right air duct temperature sensor signal with auto controls or Orange, Left side middle, Blower motor high control (C42)

“C”     Brown(2), Left upper corner, Low reference (internal ground)  lower left and right air temperature sensors with auto controls  or  Purple, Left upper corner, Medium “3” blower motor control (C42).

“D”     Red, Lower 2nd left, Battery positive voltage.

“E”      Purple, Middle 2nd left, Recirculation door POSITION signal with
auto controls  or   Tan, Middle 2nd left, Blower  motor medium “1” control (C42) RPO code.

“F”      Purple/White, Upper 2nd left, Blower control with auto controls.

“G”      Yellow, Lower 3rd left, Blower motor low control with  Manual controls.

“H”       Light Blue/Black (2), Middle 3rd left, 5 volt REFERENCE right and
left air temperature actuators.

“I”       Not used as it is easy confused with the number 1

“J”       Light Blue/Black(2), Upper 3rd left, 5 volt REFERENCE mode and
recirculation actuators.

“K”     Light Blue, Lower right corner, Medium “2” blower control (C42)

“L”      Yellow(2), Middle right, Low reference internal ground)
recirculation and mode actuators.

“M”     Yellow(2), Upper right, Low reference (internal ground)
right and left temperature actuators.

DSC09202

I did not need the following information for my situation but I decided to go ahead and post it as it may help others.

Pin designations of the C5 connector as viewed from the wire side of the connector.

“A”          Blank, Lower left corner, Not used.

“B”          Light Green, Middle left side, Mode door POSITION signal.

“C”          Tan, Upper left corner, Mode door CONTROL signal.

“D”          Dark Blue, Upper right corner, Left air temperature door
CONTROL signal.

“E”          Light Blue, Middle right side, Left air temperature door
POSITION signal.

“F”          Blank, Lower right corner, Not used.

The remaining connectors do not have any circuits related to the HVAC system.