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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4830
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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2005 Chevrolet Cobalt. About every week or so all the lights

Customer Question

2005 Chevrolet Cobalt. About every week or so all the lights on the dash come on, the steering gets hard and it starts cutting out. Disconnecting the battery will usually reset it and you may go an hour or a week before it does it again. The only code
is loss of communication with TCM . We replaced the TCM and cleaned a ground terminal at the transmission
Submitted: 2 years ago.
Category: Chevy
Expert:  Jerry Newton replied 2 years ago.
Which module was setting the TCM communication code?
Customer: replied 2 years ago.
My scanner won't tell me that but I assume it is the PCM
Expert:  Jerry Newton replied 2 years ago.
OK, so you're looking at the PCM when you get these codes. Loss of communication with TCM wouldn't kill the steering. What I suspect is that there is a larger communication issue here, something is likely killing the whole communications circuit, meaning that none of the computers can talk to each other, so they all go to default. A good quality scan tool can be helpful here, so you can see what the other computers are telling you about this issue, too. But in the end, it's usually an educated guess that gets you there, unless you can replicate the problem and pinpoint the failure. Body controller, PSCM, ABS... any of the computers on the data bus can be the culprit, you'll have to figure out which one by using the best diagnostics available. I don't think your scan tool is up to this task.
Customer: replied 2 years ago.
I have looked online and see this is a fairly common problem that nobody ever seems to fix. They get rid of the car. Considering the clues we have, what would be your best guess?
Expert:  Jerry Newton replied 2 years ago.
I've been researching a database of historical failures and fixes for this concern. TCM failure is pretty common. I also see failures of the ECM, the steering control module, and wiring issues that have fixed this problem. It depends somewhat on exactly which U codes you have, that could help to pin things down. There is some testing you can do, but you have to get it to act up. Once it's acting up, these tests are valid, but not before. 1. At key off, check the resistance between pin 6 and pin 14 of the DLC. A correct value will be 60.0 ohms +/- 10 ohms. 2. If the resistance is correct, start at the Electronic Power Steering Control Module (EPS) disconnect and bypass the module, then recheck for communicationson the TECH2 CANdi module. 3. If communications are restored, replace the Power Steering Control Module.