Car wont start, code DTC P0C76, cant reset, dealer cant fix, any luck?
Hello all, cliff notes - tried to jump my car after sitting for a week, threw code DTC P0C76, couldn't reset per the service bulletin because I dont have a Tech2 scanner. Took it to dealership, its been a week and they still cant reset the code. They contacted Gm engineers. Anyone have any luck resetting this code? Gave the tech the service bulletin I found Bulletin No.: PIT4585F Published date: 03/20/2019
Long Version:
Has anyone had this issue happen to them? Anyone find a fix? I've googlee, youtubed, etc no real luck with the same issue. I've seen some cases where people got in an accident and then the car wouldn't start, but not mine. Thank you all for any help or suggestions ! |
Re: Car wont start, code DTC P0C76, cant reset, dealer cant fix, any luck?
Your battery may have a contactor that is stuck closed:
Meaning of the code: "High voltage has been detected by the hybrid powertrain control module after the contactors have been commanded to open." "The drive motor generator power inverter module assembly (PIM) contains capacitors and a resistor circuit intended to discharge the electrical energy stored within the capacitors. Whenever the high voltage contactors are opened, the hybrid powertrain control module connects an internal resistor circuit across the high voltage positive and negative circuits. If high voltage is detected monitored by the hybrid powertrain control module after the resistor circuit has been connected, the hybrid powertrain control module commands the motor control modules (MCMs) to connect the motor phase circuits across the DC high voltage positive and negative circuits. If high voltage is monitored by the hybrid powertrain control module after the motor phase circuits have been connected, indicating a stuck-closed contactor, this DTC will set." "To clear this DTC from the hybrid powertrain control module , you must use the scan tool Special Functions, under the HPCM special functions Clear 300V Present DTC, only after the repair is complete." Open up the HV battery and check the contactors. |
Re: Car wont start, code DTC P0C76, cant reset, dealer cant fix, any luck?
How would I know if a contactor is stuck closed? Any guides online? I've seen videos of removing the batteries and replacing, but not specific to the contactor
Appreciate the help! |
Re: Car wont start, code DTC P0C76, cant reset, dealer cant fix, any luck?
This video shows where the two contactors are (negative and positive):
To test for a stuck relay, you would (after pulling the battery safety plug) test for continuity with a digital multimeter between the two main terminals of each contactor with the control lines disconnected. If there is continuity, it means it is stuck closed. It should not have continuity when there is no signal applied to the control lines. |
Re: Car wont start, code DTC P0C76, cant reset, dealer cant fix, any luck?
Originally Posted by Jaime
(Post 276431)
This video shows where the two contactors are (negative and positive): https://www.youtube.com/watch?v=nw1QzfoheaI
To test for a stuck relay, you would (after pulling the battery safety plug) test for continuity with a digital multimeter between the two main terminals of each contactor with the control lines disconnected. If there is continuity, it means it is stuck closed. It should not have continuity when there is no signal applied to the control lines. |
Re: Car wont start, code DTC P0C76, cant reset, dealer cant fix, any luck?
just like Jaime above said.
it sounds like a pretty straight forward check. I get the feeling your dealership might not have an actual hybrid guy working on your truck. I have a volt and one of those contractors went bad. they found it quicky and replaced it under warranty didn't seem like it was hard to find. I bet they have a whole walk thru troubleshooting tree to follow for that code they just aren't doing. I looked the code up on my simple non dealership level software and it gave a full test procedure, matching with he said above. you might see if you can talk to the tech directly about it without the service writer running interface. those guys are the worst, the tech will probably tell you a straight answer, or cuss you out. you can never tell what kinda day they are having lol. anyways, quick screen pic, there's like 10 more pages to validating it all and repairing it if needed. but maybe showing them they need to read the diagnostic tree will help? anyways, good luck. kinda sucks if you have to take it home to fix it, and then take it back to the dealer to clear the code. it does say the code won't clear itself in a few ign cycles like most, this one has to be manually cleared by a scanner once repair is done, it will then go thru its test and if it passes let it start. https://cimg7.ibsrv.net/gimg/www.gre...6c91376418.jpg https://cimg8.ibsrv.net/gimg/www.gre...938836661e.jpg |
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