Intermittent Electrical Issue | 2004 Chevrolet Trailblazer
2004 Chevy Trailblazer
This 2004 Chevy Trailblazer came in with multiple concerns. The main issue was intermittent low power. When this happened, the customer said that the Electronic Throttle Control, ABS, Traction Control, and sometimes the 4WD lights would come on. When the lights were on, he also stated that the cruise did not work and the HVAC and blower motor would quit working. First thing I did was scanned the truck’s multiple modules. These are the codes I found -
PCM – U1041 lost communication with ABS Module
Ignition Switch Wire Diagram
TCCM – B0790 transfer case neutral indicator circuit, C0379 front axle system, u1000 class 2 communication malfunction, u1041 lost communication with ABS Module
HVAC – B0263 HVAC actuator circuit, B1375 device ignition 3 circuit
IPC - U1041 lost communication with ABS Module
SDM - u1000 class 2 communication malfunction, u1041 lost communication with ABS Module
From the codes only I am leaning towards a bad ABS module that is bringing down the communication circuit causing the loss of throttle control. Could be a power or ground issue also. I didn’t start testing in that direction because the customer stated he would lose is blower motor control every time this would happen. That one statement changes everything because a communication problem has a low chance of bringing down a manual HVAC systems blower motor control. So I went for a wire diagram of the blower motor circuit and also the power feeds for the
Chevy Trailblazer Ignition Switch
HVAC module. Referencing HVAC code B1375, I looked for the ignition 3
Chevy Trailblazer Defective Ignition Switch
feed circuit. Fuse HVAC 1 feed that circuit. With this being an intermittent issue testing is going to be tough. So my next step is to see what feed HVAC 1 fuse and try to link that power feed to my other concerns. IGN A fuse feed to the ignition switch. From the ignition switch, power feed from the run position on circuit 300 which feeds the HVAC, 4WD, HVAC 1, Brake, and TBC Run fuses. Do you see the connection? With the ignition switch feed fuse IGN A good, the biggest common failure point would be the ignition switch. A new ignition switch fixed the customers intermittent electrical concern.
Leave any questions or comments below. Thank you.
6 comments
Good work, Thank you
ray
I have a 2007 TB LS and all of a sudden about a month ago, I am having intermittent starting problems. I have changed out the Alternator, 2 batteries, Ignition Switch and I am still having the same issues of it not wanting to start here and there. Every time I change something out it takes about a week or less and then dead again. I have noticed when it does not start, I have low lights or no lights inside of the truck as if the battery is dead. I have a drain somewhere??? I was told the battery cables could be the problem or I could have a bad starter cylinoid. I have also checked the ABS motor and made sure all lights were off when the doors close. All lights are working properly. When running, it runs perfectly. Does anyone have any other ideas?
First step in testing this that I would take is to do a parasitic draw test and see what the amperage is. Anything over 500ma is too much and I would typically see much less after pcm shut down.
Travis,
Thanks for the responce but I have no clue what you are expalaining to me. I have had the battery checked along with the new Alternator and the Volts to the battery are correct. My mechanic also volt tested everything and all seems to be functioning correctly.
You need to check for excessive battery draw and how much draw there is.
When you say check for battery draw, what am I checking and from where to where?
Thanks