Rodney: My HVAC blows hot and cold but all vents are open except driver and passenger feet vents. I bought a mode actuator but that didn’t solve the problem. I recalibrated the hvac many times via snap on scan tool. Pressing the mode button doesn’t change the vents direction. I have two codes b0159 and b3761. Help please!

Sparky: Does the display on the HVAC control head move through all of the positions with the pressing of the mode button? I understand that the airflow does not change, I just want to make sure there is not a problem with the control head.

The code B0159 is for a fault with the ambient or outside air temperature sensor. The B3761 code is for a problem with a mode door actuator. I would start with removing and reinstalling the HVAC B fuse in the rear fuse box to initiate a recalibration and not use the scan tool. Start the engine and do not touch anything. Allow the system to run for at least two minutes but no more than four. Turn the ignition off for at least ten seconds but no more than thirty. Restart the engine and check a/c operation and look for codes. My assumption is that both will return. The next step will be to make sure the correct actuator has been replaced. There are several on that side of the dash. Please provide the number off of the old actuator. If at all possible take a picture of the installed location and upload it here. Will your scan tool read HVAC data? Perform bidirectional control of actuators?

Rodney: The display moves through all of the positions. I bought a new mode actuator from The-Electric-Connection.com and according to the picture I changed the one in the middle. I did the recalibration the way you said to but no change. I still have the codes. I have a snap on Solus pro. This is the label on the actuator that I removed. Part number 52489426.

Sparky: When I looked the other day in an aftermarket source B3761 was just listed as a mode control fault. Through further research in GM SI, I found that the B3761 code is specifically related to the defrost actuator. That actuator will be located above and towards the firewall compared to the mode actuator. In the Trailblazers and Envoys the mode/vent function is split between the mode and defrost actuators.

The B0159 code is for the ambient temperature sensor located behind the grille. It has two wires: light green/black wire and a brown wire. You should be able to look at data and see the voltage and temperature data. Standard temp sensor testing. Check readings of disconnected versus jumped together. Should change between a nominal 0 to 5 volts. The key may have to be cycled between tests to get the data to update.

I have never used the Snap On Solus Pro so I will need some information from you. Can you go into Special Functions or Active Tests in order to command individual actuator movement? Can you view data stream and see actual and commanded steps? Can you see command status/voltage?

Rodney: Can you send the part number for the defrost actuator please?

Sparky: 15-72972 is the ACDelco part number.

Rodney: I tried a new air temperature sensor, so far seems to be working because the code B0159 is gone. I’m now left with the B3761. The defrost actuator counts on the scanner is at zero not moving at all.

Only code present.

Rodney: I installed the new defrost actuator and recalibrated the system. Problem is gone. Question: Why does it say drivers blend door actuator (15-72972) and not defrost actuator on everybody’s sites?

Sparky: The primary use for it is as a blend door actuator but it is used for the other applications as well. There is a very good chance that if you were to look at the numbers on the labels on your actuators (Defrost & Driver’s Temp) the numbers will match.

Marquie B: Replacing 2007 ES350 a/c evaporator this weekend. You said you learned a few things along the way. What advice would you give to help decrease the repair time?

Sparky: I would strongly recommend reading about the repair in the Lexus shop manuals. Set aside at least two days for the repair. More if you are not experienced in this kind of work. . Wear protective gloves as many parts are razor sharp. Tag, bag  and label screws in groups. Take many pictures as you disassemble so you will know how it goes back together. There is one screw that is removed from under the hood that holds the crossbar/dash to the body. Requires removal of the wiper motor assembly. After the crossbar screws are removed from the door jamb area there are inner adjustment screws that have to be loosened on the passenger side. They have allen heads.

Sherry H: I just replaced the fuse box on my 2003 Expedition with one from a 2003 Navigator due to a stalling issue. Swapped fuses from my box that were different and everything works but my battery light is on. Vehicle runs, but after about 10 minutes of driving all power to gauges, lights, etc go out, but engine is still running. No codes could be pulled, battery and alternator are fine. Info center shows there is a charging system error. Help please!

Sparky: Sounds like you are running off the battery and the battery is going dead. I would guess that either something did not get properly reconnected or the fuse box has different internal wiring circuits. You could call a Ford dealership to see if the two vehicles use the same fuse box. It would take quite a while to go through wiring diagrams to see if they are wired differently or not. You may want to install the original fuse box and see if your most recent problems go away.

Bryan C: My truck is a 2005 Chevy Silverado 2500HD WT 8.1L 6 speed manual crew cab short box….Just read about a kit for adding cruise control, very interesting….will it work with the manual transmission? I don’t know if when shifting the clutch disengages the cruise like the brake does? I’ve had older Chevy trucks with manual and cruise combo but can’t remember how it worked….any insight will be appreciated…. thanks in advance

Sparky: I have never been asked this question before but according to the wiring diagrams it should work with no problems. The clutch switch should already be installed in your truck. This is indicated by not being able to start the engine unless the clutch pedal is depressed. The clutch switch sends a signal to the PCM just as the stoplights switch does. Either signal will make the PCM disengage the cruise control.

John R: I have a 2003 Chevy Tahoe V8 5.3 liter.
I am having issues with my dual automatic climate control with temperature knobs on both sides. When adjusting the temperature knobs they don’t respond correctly. For example, turning the temperature knobs to raise temp it goes down and vise versa. Almost like stripped but not. Also when I have temperature on 80 degrees it starts off hot then after a minute or two gets air gets cooler even when at 80 degrees still. It only stays hot when on max 90 degrees.

Sparky: The knob adjustment issue is inside the control panel and is caused by non use. Sometimes all it takes is moving the knobs back and forth repeatedly to clear up the internal contact areas. If that does not work the control panel will need to be replaced.

The lack of heat issue can be caused by something as simple as low engine coolant level. Other causes would be faulty temperature sensors, doors, actuators and control systems. Other than a coolant level check the only things that can really be checked without a scan tool are the temperature reading on the rear view mirror, visually inspecting the temperature door movements and listening to the interior air temperature sensor above the driver’s head. You can also place a very light piece of paper over that vent and see if it will pull the paper up to the grill.

Kevin C: Put a good used motor in car……now when I try to start the security lite blinks (like it is supposed to) until I put in the key when I turn key to on position the only thing that comes up is the trans selector p-r-n etc but no line under the gear you’re in, no other dash lights. The fuel pump continues to run it doesn’t cycle off if no start. Also no radio …climate control comes on until you turn key to start and then it goes out…when you turn key off 3 or 4 seconds the bottom half of the dash lights up before chime goes off and interior lights come on..help!

Sparky: The first things I would suspect would be a battery with a very low charge, dirty or corroded battery terminals (especially the positive cables that are double stacked), a bad engine ground or body  ground.

What was the reason for changing the engine?

Do you have a multimeter to test with?

Kevin C:  Battery good terminals clean…all grounds(g100,g101,g102,g103,g104,g105,g106,g110) check out. My original Northstar ate a head gasket when the bypass tube clogged and it overheated… replacement motor is a runner I was pretty sure it had to be a ground but I find nothing bad unless one is hiding. I took the fuse panel in the engine compartment apart again and checked the 3 plugs and re tightened the power cables and it worked one time…pump cycled on and off tranny selector line came on radio on fuel gauge on and cranked over   but I didn’t try to start it filled fluids and now ready to start and nothing.

Sparky: What do you have to test with: scan tool, multimeter or test light?

Kevin C: I have all 3 but just to let you know my scan tool keeps saying link up problem so I assume the pcm is not sending a signal.

Sparky: I recommend starting with getting the scan tool communicating. Check to make sure there is a good ground to terminals 4 (black) & 5 (black/white) of the DLC. Also check for battery power at terminal 16 (orange) of the DLC. Be sure to check these against a known good ground. Even if you have to connect an extra wire to the negative battery terminal.

Kevin C:  I found problem…middle connector to pcm was not fully snapped into place all good now and cranking away..just wont start. I give it a shot of starting fluid and it tries to but just cant get over the hump (makes you want to grab the distributor and crank up the timing.. if it was back in the day) any ideas to get me running? Thanks

Sparky: Back to checking codes and data in the PCM. See what is there now and then disconnect both battery cables at the battery. Hold the cable ends together for about one minute. This will clear any logic lock. Reconnect the cables to the battery and see if there are any codes before and after trying to start the engine.

Kevin C: Checked codes before battery disconnect P0118, P0122, P0300, P0335, P0340, P0352, P0355, P0357, P0385, P0405,P0410, P0442 & P0741 all were confirmed and then pending and after battery disconnect they all were still there.

Sparky:

The bulk of those codes have to do with several sensors and ignition coils. To have that many real codes I would suspect one of several things.

Mismatched harnesses; was the original engine harness from your vehicle installed on the replacement engine or was used engine with it’s harness installed in your car? What year make and model of car did the donor engine come from?

Poor connection at the PCM C2 connector. Check for bent pins.

Check for 5 volt power on the gray wire at the TPS and ground on the black wire at the TPS.

Kevin C: I used the harness that came with the motor and I was told that donor car was an 04 Deville just like mine which pcm connector is c2?? The middle connector was the one that was not completely on that got me to the point I am now.  I will check voltage to tps tomorrow and let you know but in the mean time if you could let me know the c2 location?

Sparky: The C2 connector will black in color and will have 73 cavities for terminals. Not all cavities will have wires installed though.

Kevin C: I checked tps gray wire and got 4.95 volts at black. I got 9 volts(not sure I got a good probe into the black wire) when I checked the voltage at the blue wire I got 4.8 volts there at closed throttle and as throttle opened the voltage jumped around but only by a couple 10ths.

Sparky: You are missing a good ground on the black wire at the TPS. As a quick test only, add an extra ground wire to the black wire at the TPS. See if the voltage on the blue wire now responds properly when the throttle is moved.

Kevin C: We are making progress…..the c2 connector was not fully engaged…I cleared the codes and got the car started…..has a pretty good miss and wont idle unless I feather throttle let it run 5 or 6 minutes. Pulled codes again P0201, P0201, P0335, P0352, P0354 & P0358. We are getting closer want to thank you for all your help…..now lets get this puppy running good.

Sparky: The P0201 code is for a problem with the #2 injector circuit so I would check to make sure that injector harness is properly connected. You listed that code twice so I am not sure if you may have another p020? code or not? If you do check that injector as well. The p0335 code references a fault with the Crank sensor “A” (top position). Check to insure it is securely connected. The codes P0352, P0356 & p0358 are all coil codes for cylinders 2,6 & 8. Check to make sure that the coil assemblies harness is properly installed. If it is, you may want to swap the coil assembly from the other engine. Codes P0335 versus P0352, P0356 & P0358. The first code could induce the rest and the last three could induce the first.

Kevin C: I have code P0201 and P0203, so your telling me that P0201 is for cylinder 2 and then P0203 is cylinder 4?? The other P0352 and P0354 and P0358 are all on the front bank also(at least they are easy to get to) I will clear all the codes in the morning and check the connections good and fire it up. I have another coil assembly if it throws those codes again…will let you know thanks again.

Kevin C: When you say #2 injector circuit do you mean cylinder 2?? Reader said injection circuit open cylinder 1??

Sparky: Sorry my fault.  P0201 would be for injector number 1 and p0203 would be for injector number 3.

Kevin C: I will check 1 and 3 with a noid light tomorrow (is there another way?) and maybe I will put the other coil harness on the front bank.

Good news car is running and running good…..c2 connector was not making good contact…cleared all the codes and drove car half an hour now I get po123 and po405 tps and egr….I cleared these and scan tool said 1 code remained rerun the codes and I cant get rid of the po123..why wont it erase??

Sparky: The code setting criteria for P0123 is that the PCM sees 4.7 volts from the TPS for more than 1 second. If you can see data stream in your scan tool monitor this voltage and compare it to actual measurement at the TPS. If you cannot see data you will need to check the signal wire at the PCM and compare it to the reading at the TPS. You can also disconnect the TPS connector and run the vehicle for a little while and see if the code shifts to a P0122, signal voltage less than .16 volts for more that 1 second.

Kevin C: Everything is working out pretty good on my 04 Deville, I was having po123 codes and po405. I replaced the tps plug and got rid of the po123. Now for the po405, I clear the codes and the mil light goes off but code reader says 1 code remaining… I can drive the car 30 miles and the mil light wont come on until I shut it off. When I restart…there it is again(mil) with po405 any advice???

Sparky: Can your scan tool read data and perform bidirectional controls?

Kevin C:  It reads data and has a freeze frame function but no bidirectional codes…..

Sparky: The P0405 code sets when the EGR valve position sensor is less than .11 volts for more than two seconds. Start by monitoring that data and see if the voltage is indeed low. Closely inspect the EGR valve terminals to see if any are damaged. If damage is found repair and re test. If no damage is found disconnect the EGR harness and check data. It should be near 0 volts. Using a 3 amp fused jumper wire connect the Brown wire at terminal C to the Gray wire at terminal D. Check the reading it should be near 5 volts. There are two gray wires at the EGR harness. Make sure it is terminal D. If your readings were good more than likely the EGR valve itself is faulty. Beyond this test you really do need bidirectional controls or at the very least a really good multimeter, backprobe connectors, time and patience.

Kevin C: OK… that code may have to wait. Thanks again…your help has been invaluable

Jason M: I need help with my 05 Trailblazer a/c. It started blowing hot air on the passenger side and the rear while blowing cold on the driver side. When I turn the vent on it just blows defrost and on the floor.

Sparky: It sounds like the battery may have been recently disconnected and the system did not properly recalibrate. I would start by performing a recalibration. Remove the HVAC B fuse in the rear fuse box for one minute. Reinstall the fuse and then start the engine. DO Not touch anything and allow the engine to run for at least one full minute. Turn the ignition off for at least ten seconds but no more than thirty seconds. Restart the engine and check the system performance. If you still have a problem it is likely that you have faulty actuators. The mode actuator in particular is very common to fail.

Jason K: Where is the fuse that control the sun visor lights on my 2005 Tahoe and do you know what size ….. thanks

Sparky: The vanity lights are supplied power from the BCM on the orange wire. The BCM is supplied power on multiple TBC fuses in the underhood and interior fuse boxes. The overhead MAP and Reading lights are also supplied power from the orange wire. If they work the BCM is okay and you have either a wiring problem on the power side or a lack of ground on the black wire.