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:

• 2009 Escalade sat for a week, battery was drained, didn't want to start.
• Tried to jump the car with my other car, no luck.
• Saw the car had a code, scanned it, and I looked online.
• Realized there was a service bulletin, realized I couldn't reset myself because it requires a Tech 2.
• Took my battery to autozone, got it fully charged, went back home and tried to reset anyways, no luck.
• Tuesday Took car to the dealership, they said if quick reset theyll get it done in a day if not they'll put it in the queue. Sat there for 2 days, they called me and said I needed a new car battery, told them i just had it fully charged. They told me they would charge it.
• Friday They told me tech would not go any further unless I purchase a new battery. I told them if the tech cant fix it with their new battery im not paying for it. They said they cant return it once its been installed. Told them to proceed.
• Monday and Tuesday no got busy at work didn't call them, they didn't call me.
• Wednesday they tell me tech is working on it, code reset isnt working for them either. Noticed a shock code as well (ive had it for over a year, even with brand new gm rear air assisted shocks). Told them that did not have any issues in the past. They told me to give them another day.
• Thursday they said the Tech needs one more day, can't figure it out, its 4pm, I told them are you really working on it, or just pulling my leg? If they are busy with other cars I understand but just need a status update. They told me they would give me one the following day at the same time, I told them it shouldn't take over 8 hours to troubleshoot a code like this (I work on cars too). They said ok call you at 2pm.
• Friday at 3pm I receive a call, tech told the service manager he's reached out to GM engineering and isn't able to fix the issue.

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 !

 

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.

 

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!

 

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.

 

Thanks for the tips! If dealer returns car to me without fixing it, I'll try that!

 

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.