Page 26 – Sparky's Answers

These posts will apply to to the midsized SUV’s listed below. There will be slight differences between brands and year models. Year model 2002 mode actuators are different from all other years and so is the procedure. I have not had the opportunity to document one of these yet. If the vehicle has adjustable pedals the accelerator pedal assembly may have to be removed.

2003 GMC Envoy, No A/C Vent Control, B0263

2004 Chevrolet Trailblazer, Identifying The Heater- A/C Actuators On Driver’s Side

2002 Chevrolet Trailblazer, Poor Heat, Clicking Sound Under Driver’s Side Of Dash

HVAC Calibration Procedure GM Trucks And SUV’s

1999 Chevrolet 1500/2500 Pickup, New Body Style

1999 GMC 1500/2500 Pickup, New Body Style

2000 Chevrolet Silverado
2000 Chevrolet Suburban
2000 Chevrolet Tahoe
2000 GMC Sierra
2000 GMC Yukon

2001 Chevrolet Silverado
2001 Chevrolet Suburban
2001 Chevrolet Tahoe
2001 GMC Sierra
2001 GMC Yukon

2002 Cadillac Escalade
2002 Chevrolet Avalanche
2002 Chevrolet Silverado
2002 Chevrolet Suburban
2002 Chevrolet Tahoe
2002 Chevrolet Trailblazer
2002 GMC Envoy
2002 GMC Sierra
2002 GMC Yukon
2002 Oldsmobile Bravada

2003 Cadillac Escalade
2003 Chevrolet Avalanche
2003 Chevrolet Silverado
2003 Chevrolet Suburban
2003 Chevrolet Tahoe
2003 Chevrolet Trailblazer
2003 GMC Envoy
2003 GMC Sierra
2003 GMC Yukon
2003 Isuzu Ascender
2003 Oldsmobile Bravada

2004 Buick Rainier
2004 Cadillac Escalade
2004 Chevrolet Avalanche
2004 Chevrolet Silverado
2004 Chevrolet Suburban
2004 Chevrolet Tahoe
2004 Chevrolet Trailblazer
2004 GMC Envoy
2004 GMC Sierra
2004 GMC Yukon
2004 Isuzu Ascender
2004 Oldsmobile Bravada

2005 Buick Rainier
2005 Cadillac Escalade
2005 Chevrolet Avalanche
2005 Chevrolet Silverado
2005 Chevrolet Suburban
2005 Chevrolet Tahoe
2005 Chevrolet Trailblazer
2005 GMC Envoy
2005 GMC Sierra
2005 GMC Yukon
2005 Isuzu Ascender

2006 Buick Rainier
2006 Cadillac Escalade
2006 Chevrolet Avalanche
2006 Chevrolet Silverado
2006 Chevrolet Suburban
2006 Chevrolet Tahoe
2006 Chevrolet Trailblazer
2006 GMC Envoy
2006 GMC Sierra
2006 GMC Yukon
2006 Isuzu Ascender

2007 Buick Rainier
2007 Chevrolet Silverado Classic
2007 Chevrolet Trailblazer
2007 GMC Envoy
2007 GMC Sierra Classic
2007 Isuzu Ascender

2008 Chevrolet Trailblazer
2008 GMC Envoy
2008 Isuzu Ascender

2009 Chevrolet Trailblazer
2009 GMC Envoy

Blower Motor Systems For GM Manufactured Trucks, SUV’s and Vans 1995-2012

I have separated the information that I have for the model years 1995 through 2012. This list covers the following model trucks, suv’s and vans that were made by General Motors but sold under the Buick, Cadillac, Chevrolet, GMC, Isuzu, Oldsmobile and Saab brands.

The following list of vehicles use the same blower resistor and blower speed switch. Therefore the three part repair posts that I have linked to apply to all on the list. Not just the vehicle in the post title.

1997 GMC 1500 Blower Does Not Work Part 1

1997 GMC 1500 Blower Does Not Work Part 2

1997 GMC 1500 Blower Does Not Work Part 3

1998 Chevrolet C1500 Changing The Blower Motor Assembly

1995 Chevrolet C&K Pickup 1500/2500/3500
1995 GMC C&K Pickup 1500/2500/3500
1995 Chevrolet C&K Suburban
1995 Chevrolet C&K Tahoe
1995 GMC C&K Pickup 1500/2500/3500
1995 GMC Yukon

1996 Chevrolet C&K Pickup 1500/2500/3500
1996 GMC C&K Pickup 1500/2500/3500
1996 Chevrolet C&K Suburban
1996 Chevrolet Tahoe
1996 GMC C&K Pickup 1500/2500/3500
1996 GMC Yukon

1997 Chevrolet C&K Pickup 1500/2500/3500
1997 Chevrolet Suburban
1997 Chevrolet Tahoe
1997 GMC C&K Pickup 1500/2500/3500
1997 GMC Yukon

1998 Chevrolet C&K Pickup 1500/2500/3500
1998 Chevrolet Suburban
1998 Chevrolet Tahoe
1998 GMC C&K Pickup 1500/2500/3500
1998 GMC Yukon

1999 Cadillac Escalade w/manual controls
1999 Chevrolet C&K Pickup 1500 Old Body Style
1999 Chevrolet C&K Pickup 2500/3500
1999 Chevrolet Suburban
1999 Chevrolet Tahoe
1999 GMC C&K Pickup 1500 Old Body Style
1999 GMC Yukon

2000 Cadillac Escalade w/manual controls
2000 Chevrolet C&K Pickup 2500/3500
2000 Chevrolet Suburban
2000 Chevrolet Tahoe
2000 GMC C&K Pickup 2500/3500
2000 GMC Yukon

2001 Chevrolet C3500
2002 Chevrolet C3500

The following full sized trucks and suv’s with manual a/c controls all use the same series of blower systems. Testing and replacement of the blower resistors are the same. There are minor variations in the blower motor replacements.

2000 Chevrolet Silverado Changing The Cabin Air Filter

2002 GMC Sierra, Blower Works Sometimes

2003 Chevrolet Suburban, No Blower Speeds 2 and 4

2003 Chevrolet Silverado, Blower Does Not Work On Any Speed

2003 Chevrolet Trailblazer, Blower Does Not Work on Any Speed

2005 Chevrolet Silverado, Blower Inop Most Read

2007 Chevrolet Silverado Classic, Changing The Blower Motor

Identifying The Correct Blower Resistor For Your 1999 – 2007 Classic Series Truck

1999 Chevrolet 1500/2500 Pickup, New Body Style
1999 GMC 1500/2500 Pickup, New Body Style

2000 Chevrolet Silverado
2000 Chevrolet Suburban
2000 Chevrolet Tahoe
2000 GMC Sierra
2000 GMC Yukon

2001 Chevrolet Silverado
2001 Chevrolet Suburban
2001 Chevrolet Tahoe
2001 GMC Sierra
2001 GMC Yukon

2007 Buick Rainier
2007 Chevrolet Silverado Classic
2007 Chevrolet Trailblazer
2007 GMC Envoy
2007 GMC Sierra Classic
2007 Isuzu Ascender

2008 Chevrolet Trailblazer
2008 GMC Envoy
2008 Isuzu Ascender

2009 Chevrolet Trailblazer
2009 GMC Envoy

This information is for the rear blower systems with manual a/c controls on the following vehicles.

2004 Chevrolet Tahoe Rear Blower Will Not Turn Off

2000 Chevrolet Tahoe
2000 GMC Yukon

2001 Chevrolet Tahoe
2001 GMC Yukon

2002 Cadillac Escalade
2002 Chevrolet Tahoe
2002 GMC Yukon

2003 Cadillac Escalade
2003 Chevrolet Tahoe
2003 GMC Yukon

2004 Cadillac Escalade
2004 Chevrolet Tahoe
2004 GMC Yukon

2005 Cadillac Escalade
2005 Chevrolet Tahoe
2005 GMC Yukon

2006 Cadillac Escalade
2006 Chevrolet Tahoe
2006 GMC Yukon

This information is for trucks and suv’s with auto a/c controls in the list below.

2003 Chevrolet Silverado Blower

2003 GMC Yukon Blower is Erratic/Not Working (Updated part information applies to all on list.)

2004 Chevrolet Silverado, Blower will Not Turn Off

2007 Chevrolet Silverado Classic, Changing The Blower Motor

2003 Cadillac Escalade
2003 Chevrolet Avalanche
2003 Chevrolet Silverado
2003 Chevrolet SSR
2003 Chevrolet Suburban
2003 Chevrolet Tahoe
2003 Chevrolet Trailblazer
2003 GMC Envoy
2003 GMC Sierra
2003 GMC Yukon
2003 Isuzu Ascender
2003 Oldsmobile Bravada

2004 Buick Rainier
2004 Cadillac Escalade
2004 Chevrolet Avalanche
2004 Chevrolet Silverado
2004 Chevrolet Suburban
2004 Chevrolet SSR
2004 Chevrolet Tahoe
2004 Chevrolet Trailblazer
2004 GMC Envoy
2004 GMC Sierra
2004 GMC Yukon
2004 Isuzu Ascender
2004 Oldsmobile Bravada

2005 Buick Rainier
2005 Cadillac Escalade
2005 Chevrolet Avalanche
2005 Chevrolet Silverado
2005 Chevrolet Suburban
2005 Chevrolet SSR
2005 Chevrolet Tahoe
2005 Chevrolet Trailblazer
2005 GMC Envoy
2005 GMC Sierra
2005 GMC Yukon
2005 Isuzu Ascender
2005 Saab 9-7X

2006 Buik Rainier
2006 Cadillac Escalade
2006 Chevrolet Avalanche
2006 Chevrolet Silverado
2006 Chevrolet Suburban
2006 Chevrolet SSR
2006 Chevrolet Tahoe
2006 Chevrolet Trailblazer
2006 GMC Sierra
2006 GMC Yukon
2006 Isuzu Ascender
2006 Saab 9-7X

2007 Buick Rainier
2007 Chevrolet Silverado Classic
2007 Chevrolet Trailblazer
2007 GMC Envoy
2007 GMC Sierra Classic
2007 Isuzu Ascender
2007 Saab 9-7X

2008 Chevrolet Trailblazer
2008 GMC Envoy
2008 Isuzu Ascender
2008 Saab 9-7X

2009 Chevrolet Trailblazer
2009 GMC Envoy
2009 Saab 9-7X

The following repair information is for small trucks made by General Motors from 2003-2012 with manual a/c controls.

2005 Chevrolet Colorado Blower Only Works on High

2003 Chevrolet SSR

2004 Chevrolet Colorado
2004 Chevrolet SSR
2004 GMC Canyon

2005 Chevrolet Colorado
2005 Chevrolet SSR
2005 GMC Canyon

2006 Chevrolet Colorado
2006 Chevrolet SSR
2006 GMC Canyon
2006 Isuzu I-280 & I-350

2007 Chevrolet Colorado
2007 GMC Canyon
2007 Isuzu I-290 & I-370

2008 Chevrolet Colorado
2008 GMC Canyon
2008 Isuzu I-290 & I-370

2009 Chevrolet Colorado
2009 GMC Canyon

2010 Chevrolet Colorado
2010 GMC Canyon

2011 Chevrolet Colorado
2011 GMC Canyon

2012 Chevrolet Colorado
2012 GMC Canyon

The following information is for 1996-2005 Chevrolet Astro and GMC Safari vans.

1998 Chevrolet Astro Van Blower Only Works On High

The following information is for 1996-2002 Chevrolet Express and GMC Savana vans.

1997 GMC Savana Van Changing The Blower Resistor

I hope that this will make finding the needed information much easier.

1995 Infiniti J30 Replacing The Blower Motor

This 1995 Infiniti J30 came in with a faulty blower motor assembly. The blower motor is located under the passenger side of the dash.

There are a few screws and snaps that hold the lower cover in place.

A courtesy light also has to be unplugged.

There are screws at either side of the glove box opening, 10 mm. there may be small covers over the screw heads.

The passenger side kick panel has to be removed. There is a nut at the rear edge and a screw at the top edge.

The vertical portion of the rocker panel or sill plate will need to be unclipped as well.

In order to access and remove the blower motor the computer will have to be removed. I started by loosening the 10 mm screw that attaches the harness connector to the computer.

With the connector out of the way I used a 10 mm wrench to loosen and remove the two screws that hold the bracket on place. This bracket is in the way of removing the computer.

There is a screw at the bottom under the carpet that needs to be removed.

One behind the carpet at the firewall edge.

Then the computer can be rocked down from the upper retaining bracket.

The computer can now be fully removed.

Now the upper retaining bracket for the computer has to be removed. Two more 10 mm screws.

There is one small phillips headed screw that is up in a tight location as shown below.

The small screw removed.

There are three more phillips headed screws that need to be removed. They are easy to access and have a slightly different design.

There is one piece of linkage that is attached to the lower left corner of the panel as shown below. It has a flip door latch that has to be opened in order to remove the threaded rod linkage.

The next picture shows the location of the mounting hole that is next to the inner kick panel. I had to feel around for the screw and then slide the screwdriver into position.

Now that the cover panel has been removed the blower motor assembly can be removed by taking out it’s four mounting screws. The blower motor in the next picture is actually the new motor as it is getting ready to be installed.

Due to the difference in connector locations on the old and new motors, I had to extend the length of the two wires by about six inches.

The old blower motor on the left and the new one on the right.

I could not install the less expensive aftermarket design blower motor as it is designed to replace the motor only. The fan blade and the mounting plate are intended to be reused after inserting the new motor into it. The problem is that the new motor has a nominal outside diameter of 3.25 inches and the old motor insert is only 2.75 inches in diameter.

The high blower relay.

Due to the length of this repair post I will be breaking it up into at least two posts. To see the diagnostic part of this repair please click here.

2004 Honda Accord 3.0 Liter V6 Misfires

This 2004 Honda Accord came in with the SES (or check engine) light on. I checked codes and found a misfire code for everyone of the six cylinders. P0301, P0302, P0303, P0304, P0305 and P0306. With a code set for every cylinder plus a random misfire code P0300 I was pretty sure there would be a common fault to all.

The fault as it turned out was the previous repair done by the inexperienced son of the owner. Since I was looking for a common thread and suspected a problem with the spark plugs themselves, I asked the customer if the spark plugs had been replaced anytime in the recent past. She acknowledged that her son had installed new spark plugs about a year ago. I started at the forward cylinder head. The black plastic cover is held on by two screws at either end.

With the cover out of the way, I disconnected the ignition coil harness connectors.

Loosened the coil retaining bolt.

Removed the bolt and pulled the coils out.

The rusty looking deposits on the coil boot is from combustion gases.

More deposits.

The seal at the porcelain base to the steel housing appears to have been leaking combustion gases.

However I was also able to remove the spark plugs using my ratchet as shown in the next picture. The spark plugs were not properly tightened when they were replaced.

Looking at the spark plug crush gasket, I could see that it had never been crushed.

To show the difference in the crush gaskets, I tightened the plug on the left to the proper torque before removing it.

The properly tightened spark plug gasket measures 1.83 mm in thickness.

The one that was not fully tightened measures 2.18 mm in thickness.

It is a little hard to see but I try to always use a torque wrench when tightening anything on an engine. Including spark plugs. I prefer the clicker type torque wrenches. The specifications for the spark plugs on this engine are 13 ft lbs. Please check the specifications for yours.

The torque specs for the ignition coils was 8.7 ft lbs.

After properly installing a new set of spark plugs and clearing the codes, all is well with this Honda. In case you are wondering, the slightly loose spark plugs were not properly grounded and this was triggering the misfire codes. The problem was slight enough that I could not feel the misfires but the PCM was picking up on them. I am sure an oscilloscope would have picked it up but no sense in adding cost to the repair as it was simple and evident.

2005 Chevrolet Suburban Instrument Cluster Does Not Work

This 2005 Chevrolet Suburban came in with the complaint that the instrument cluster gauges do not work. I asked the customer how the problem had started and he told me that the speedometer has been acting up for a while. Recently all of the gauges stopped working at the same time. I connected my Tech 2 scan tool and checked IPC codes and data. The IPC would not communicate at all. In checking power supplies to the IPC on a wiring diagram I found that thee are multiple designations for the battery all the time and ignition fuses. The continuous battery fuse may be labelled IPC/DIC, 10 amp or SEO B1, 15 amp. The ignition fuse may be labelled IGN E or SEO IGN. Both are 10 amp fuses.

The troubling thing is all four are listed in the fuse box legend. I checked the IPC/DIC fuse as shown below.

The IGN E fuse tested good as well. The key had to be good in order to confirm power was present on both legs of the fuse. Since the other two fuses were also installed in the fuse box I checked those as well and the too were okay and had the proper power signal present.

Now I had to check for the same power conditions at the wiring harness behind the instrument cluster. The next step was to remove the dash trim panel that covers the IPC. I always start by grasping the outer edge of the panel and pull it out to release the spring clips.

The steering column will need to be tilted fully down and the shifter placed in the lowest gear setting. Then the trim panel has to be carefully rolled out of the dash. The hazard switch will likely pop up and will have to be turned back off.

Four screws hold the IPC in place and they all have 7 mm heads. Once the screws are removed the cluster can be rolled towards the steering wheel and the harness disconnected.

The IPC harness connector.

Battery power is supplied on the orange wire, terminal B11.

Ignition power is supplied on the pink wire, terminal B9.

There are two ground wires, terminal A12 and terminal B12. Both wires are black and one has a white stripe.

I alternated using the A12 and B12 terminals for a ground and tested power at both B9 and B12 using a jumper wire assembly with a halogen headlight bulb installed. This provides a load on the circuit. I often will use a fused jumper wire with the factory rated fuse installed and I install a slightly higher amperage fuse in place of the original factory fuse for the circuit. I actually prefer that as it will accurately tell me if a wire pair will carry the factory rated amperage. In this case 10 amps. Hard to capture the fuse blowing on camera though. Either one of these tests are not for the faint of heart or the uneducated. The bulb can shatter, melt plastic or burn skin. Jumping power and ground circuits can immediately destroy components, releasing the magic smoke that allows all electronics to function.

The next step was to isolate the data communication line between the IPC and the splice pack the the lower left of the dash assembly. I removed the white buss bar and located the gray wire at terminal “G”. I installed a test lead to insure a good connection.

I checked for a short to power or ground using my ohm meter, okay.

I then checked continuity from the IPC terminal A6 to the splice pack terminal “G”. It too was okay.

Diagnosis of a faulty instrument cluster assembly. Replacing the IPC involves some programming and that is a topic for another day.

2005 Chevrolet Tahoe, No or Erratic Heat

This 2005 Chevrolet Tahoe came in with the complaint that the heater was working erratically. The customer stated that when she started the engine in the morning there would be no heat while idling and driving down her driveway. Once she had been driving at highway speed for several minutes heat would start coming out. When she got in traffic it would come and go. She thought that her Tahoe had some sort of terrible electrical problem.

Well, it turned out that the main problem was that the coolant level was low by one gallon. The coolant reservoirs become stained over time with neglect and at first glance it looks like there is something in the reservoir.

You can see the color change slightly above the halfway seam in the tank.

Removing the pressure cap (following proper safety procedures) revealed that there was no coolant on the reservoir tank. You may need to click on the picture below to enlarge it, to be able to see.

I installed a 50/50 mixture of Dexcool and distilled water. It took one gallon.

You can see the shadow is now darker and you can see some orange color in places.

A much better view of the coolant level from the driver’s side of the vehicle.

Another view from the firewall side of the tank. This is the general full level for a warmed up engine.

I did a little bit of checking and found a coolant leak at the heater hose tee where it connects to the front heater core and the lines for the rear heater core. Normally a leak in this area would be attributed to a leaking intake gasket but not so in this case. The drip on the ground was at the passenger rear side of the engine and that is where a leaking intake gasket normally drips on these engines.

She says she will have me change the tees and heater hose connectors but we will have to wait and see.

1996 Chevrolet S10, Air Blows Out Of The Defroster Only

This 1996 Chevrolet S10 came in with the complaint that the heater/ air conditioner air only blows out of the defroster vents regardless of where it is commanded. It is actually a pretty simple problem and strangely enough it is not an electrical problem. The most common place for failure is in the under hood vacuum hoses that attach to the vacuum reservoir.

If you look closely at the picture below you should notice that one of the vacuum hoses is flat.

You can barely see it but the shorter hose has a split on the underside of it, at the curve.

The vacuum supply hose is attached to the engine (V6, VIN X) at the PCV housing. Removing the breather elbow at the throttle body makes it easier to gain access to it.

I am using a large flat blade screw driver to push the hose off of the nipple. A little bit at a time and switching sides. I did not want to break anything.

The vacuum supply hose removed from the engine. Small hose at the center of the picture.

There are two sizes of vacuum hoses used for this repair, 5/32 and 7/32.

All new hoses attached to their respective parts.

This repair applies to several different models and years. I think it was for year models 1994, 1995, 1996 & 1997. It applies to Chevrolet S10 pickups and Blazers. Along with GMC S15 pickups and Jimmy. Hopefully some one out there will help clarify this for us.

2004 VW Beetle, Low Beam Headlight Works Sometimes

This 2004 Volkswagon Beetle came in with the complaint that the passenger side low beam headlight works sometimes. I suspected a loose or burnt terminal inside the headlight assembly. This vehicle had been wrecked somewhere along the way and the mounting locking tab was broken so it is being held in place by a screw. If you want to see how to take out a complete assembly please see the information at this link.

Once the headlight assembly is out of the car it is simply a matter of removing one small screw (if present) and depressing the locking tab on the black cover.

With the cover out of the way it is pretty easy to see the damaged wiring. If needed click on the pictures to enlarge them.

Some one had been in there before and had used electrical tape to insulate the bare wires. Okay for a temporary fix but not the long term. They would have been better off using a pair of pliers to tighten the female spade terminals.

Anyways I installed a new bulb and harness connector with and extra ground wire.

The thing that I really like about this connector is that it has an extra ground wire built into it and the center terminal attaches very tightly.

These bulbs tend to develop problems due to loose mounting clips and weak ground terminals.

You can see in the pictures that the outside tabs give a lot of contact area for the ground supply to the bulb.

The installed height of the connector assembly is 1.204 inches.

Or 30.59 mm.

As measured from the base of the bulb in the picture below. I know for sure it will fit this application but the H1 bulbs are used on many vehicles. To order these connectors please click here.

2005 Chevrolet Tahoe, Multiple Complaints, Communication Faults

This 2005 Chevrolet Tahoe came in with multiple complaints. Radiator cooling fans on with key off, dash warning lights on, gauges not working, door locks cycling, power windows not working and of course the battery will go dead if left sitting for any length of time. I had checked this Tahoe out a few weeks earlier and knew it had a PCM problem. Since it had under 65,000 miles the PCM was still under warranty, I sent the customer to the dealer for repairs.

Sadly the Tahoe is back at my door. According to the customer the dealership had replaced the PCM and refused to do anymore work to the Tahoe. Sounds like a lack of communication to me. More than likely the dealership informed the customer of a deeper problem and the customer refused to pay for any other repairs. Not knowing how much of the story was true, I checked to make sure the PCM had been replaced. Looks like a new install to me.

The first time I saw this Tahoe the only problem it had was the battery was going dead from the engine cooling fans staying on sometimes with the key off. Now there was a growing list of symptoms. I checked codes using my Tech 2 scan tool and found multiple class 2 data communication fault codes. I performed a Class 2 DTC check to see how many modules were in this vehicle. I repeated the check several times over a five to fifteen minute span with the engine running. I found a range of seven to eleven modules reporting during the various times I checked Class 2 DTC’s. Time to access the class 2 data junction or buss bar. It is located under the driver’s side of the dash. The covers do not have to be removed but it makes it a little easier to see things if you do.

Remove a couple of 7 mm headed screws at the lower edge and the panel will unsnap from the dash.

The connector I was looking for is about three inches above my hand in the picture below. The wires that I am holding are just part of a harness that was in the way for taking a picture. The connector body is taped to a harness. The tape has to be undone or cut to get the connector and its short harness down for testing.

The class 2 data connector pulled down from the dash for easier access to the wiring. I sure do wish the engineers would have added a few more inches of wire to the harness though.

My next step was to use a small screw driver to remove the connecting bar, shown below.

Now the fun begins. I had to carefully insert my test lead assembly into the connector body. This lead assembly takes the place of the little white buss bar.

All of the wires leads are installed into the connector body except for one. Even though there are twelve spaces only eleven wires are installed.

With any kind of computer issue the two of the most important tools are a pen and paper. As mentioned earlier I looked for Class 2 Data DTC’s, one of the chief reasons for doing this is to see how many modules are reporting at any given time. Doing this allows me to build a written list of modules. With the full list built it is just a matter of repeating the same Class 2 DTC test to see which modules go missing. In this case the PCM, ABS, SIR and GBCM modules would drop out on a fairly regular basis.

While monitoring Class 2 Data DTC’s and looking for changes in vehicle behavior. I disconnected one wire at a time with the engine running and checked for reactions. I only had to do this with the four terminals associated with the missing modules from my list. My initial testing and subsequent list eliminated almost 65% of the testing possibilities.

Using a wiring diagram that shows the Class 2 data lines, I knew what color wires were involved and their positions within the connector body. The connector body has letter designations for each terminal.

I know you were hoping to read the diagram but it is a licensed product and I do not own the license to share it with you. If you want it you have to buy it just like I had to.

The Tech 2 screens involved in getting to Class 2 DTC tests.

In the end the problem was with the PCM communication line. Water had gotten into the lower half of the blue, C2 connector and left corrosion. When the dealership had replaced the PCM under warranty, the tech thought he was doing an extra good service by adding a dielectric gel/grease to the connector. What in fact happened was a conductive gel was created in the connector between the terminals.. This conductive gel was driving the computer system crazy with false readings. The best fix for the problem would be to replace the PCM and the engine harness. The customer did not have the money to do this so I removed the blue cover and using a small bristle brush I cleaned the mess from the connector. I dipped the brush into an electrical contact cleaner and wiped all of the contaminant away. After it was cleaned I checked to see if any terminals were damaged and found nothing of significance. I installed the blue locking cover and wiped a slight amount of grease into the small holes. I checked the gasket for damage and found none. I flipped the gasket over from its original position and rubbed it down with dielectric grease for an added seal.

I informed the customer of the situation and we agreed that we will monitor the integrity of the seal and connector over the coming months. I also advised them to get their finances prepared for replacing the harness and PCM in the near future.

They stated that they were also going to contact GM about the issue. I wished them luck.

2001 Buick Park Avenue, Multiple Electrical Problems

This 2001 Buick Park Avenue came in with multiple complaints. Some of which were various dash warning lights would come on, the gauges would stop working, the power door locks would cycle intermittently and the battery would go dead. I asked the customer specifically if the clock on the radio would reset and was relieved to hear the answer was yes. Experience has taught me that if the clock resets that there is likely to be a major power or ground circuit interruption. I did a quick voltage check at the battery with the engine running. A flat 12 volts indicated there was a problem.

I checked the voltage at the junction stud connection on the underhood fuse box and it was what I should have expected with a running engine. A nominal 14 volts.

It seemed to me that with normal voltage at the fuse box stud, low voltage at the battery positive terminal and an obvious junction point in between, that the junction point may be the location of the problem.

At first glance there did not seem to be a problem at the junction point. No arc or burn marks were present.

A gentle wiggle of one of the cables indicated that it was indeed loose. Notice that my fingers are back on the insulation and not on the terminal itself. Experience is a mighty fine teacher.

I decided to take a temperature reading to show why I did not just carelessly grab the terminal. The engine had only been running about three minutes when I took the reading with my infrared heat gun. Amperage plus resistance equals heat and a lot of it.

I turned the engine off and let the connector cool down for a while. Then I took the connector apart, wire brushed the terminals and tightened the nut securely. I took another temperature reading. Roughly two hundred and sixty degrees cooler than before.

At start up the battery terminal voltage was 13 volts. It did not start coming up very quick so I turned the engine back off and connected a battery charger to the car.

After all alternators are designed to keep a fully charged battery fully charged. They are not designed to recharge a discharged battery.