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r/volt•
BetterWithoutThis

2012 Engine Unavailable. Error codes: P0507, P0700, P079c

A few nights ago, I was driving in ICE mode, at 45 mph with cruise set, and the vehicle began to "surge" forward then coast in rapid succession; it felt like the car was rocking back and forth. After a few miles, the engine began to rev very high and the check engine light fired on and I received the Engine Unavailable/Limited Propulsion notice. At that point, I pulled over and got a tow home as I was too far to make it in limp mode. Got it home, pulled the codes and checked the 12v (it's fine). After a full charge, the codes cleared and the vehicle operated normally in EV mode. Well, driving home last night and as soon as the ICE kicked on, the engine revved really high and the car started throwing codes again and entered limp mode. Any ideas or experience with this issue? I'm having trouble finding anything solid here or on the Volt forum.

Error codes: P0507, P0700, P079c

Posted Apr 14, 2018, 10:44 PM UTC

814
Isitharry•

I have the factory manual for the 2012. It's 4 volumes and over 6 inches in overall thickness. FYI, most code readers are not able to read ALL codes produces. Anyhow, here goes:

DTC P0700 is an informational DTC, indicating an emissions related transmission DTC set in the TCM.

DTC P0507 is the IAC RPM too high. The actual engine is approximately 150 RPM greater than the commanded engine speed. Verify/check vacuum leaks, throttle valve not closing correctly and PVC system.

DTC P079C is Transmission clutch 3 slip detected. This is involved. Transmission fluid level and condition check, line pressure check to verify oil pressure and operate in LS-ICE where clutch 3 slip speed should be less than 100 RPM when clutch 3 is applied. Next are control solenoid valve and transmission control module inspection and performance check for condition and function, check the a/trans fluid level control valve for stuck closed/damaged condition, inspect control valve body spacer plate assembly, 1-3 reverse and drive motor/generator ststor cooling regulator valve and its feedback valve, and inspecting the 1-4 reverse clutch assembly, piston, snap ring, discs and housing.

There were portions in the manual about the diagnosis if there were other listed DTC present. I omitted them as you didn't get those.

Good luck!

9
BetterWithoutThisOP•

Thanks for the info. I have an appointment at the dealership to get it checked out.

1
geo433Volt Owner/Tech•

More than likely it will need the Control Solenoid Valve Assembly/TCM replaced. Not the first time I see those codes pop up. Have it towed to the dealer. It will be covered under your 8 yr/100,000mi Voltec Warranty.

4
BetterWithoutThisOP•

Thanks for reply. I'm going to take it in for service. Is there anywhere the Voltec warranty is spelled out? There seems to be a lot of confusion online over what is covered or not.

1
geo433Volt Owner/Tech•

Yes there is. In service information the labor operation for a TCM replacement shows it is covered under Voltec warranty. Feel free to send me your vin and mileage if you want to know what coverages you have left.

1
BetterWithoutThisOP•

Thanks again, PM sent with the info

1
BetterWithoutThisOP•

Just got my Volt back after 5 weeks at the dealership. My service rep was not very helpful and not there when I picked up the car. Would you mind looking over the service performed and giving me the laymen's rundown? Anything to worry about in the future? Thanks again.

https://imgur.com/a/1f97FdW

1
geo433Volt Owner/Tech•

It looks like they definitely replaced the (TCM)Transmission Control Module Assembly and also other failed internal transmission parts due to the TCM not correcting your concern.They called (TAC) Technical Assistance Hotline for help on correcting your concern. That is normal and we normally call TAC for expensive repairs or hard to fix concerns since GM wants the correct fix on the first visit. They also reprogrammed your (HPCM2) Hybrid Powertrain Control Module 2, which wont make a difference in your concern, but we do it to make sure you have the latest programmings installed in your vehicle. I would say they did the proper repair and you should not have any more issues with the Transmission. I don't understand why they decided not to give you a proper explanation. Make sure to submit your feedback when you get a survey in your email or mail. Most stores take their (Customer Service Index)CSI score very seriously. I am certain that you should have no issues, but if you do let me know and I can give you an idea of what's going on so you have a clue before you take it in for service.

1
ochaosVolt Owner•

This is what I've found.

  1. P0507 - Idle Control System
  2. P0700 - Transmission Control Module(TCM) Requested
  3. P079C -Transmission Clutch 3 Slip Detected

Yeah, something's wonky there. I'd take it to a dealer or another mechanic with Volt specific knowledge.

2
jamesgor13579Volt Owner•

I think the clutches in the Volt are supposed to be engaged or disengaged, never slipping. Clutch 3 is the clutch from the ICE to Motor/Generator A. That explains why it works fine on battery. You need to take it to a dealer.

3
BetterWithoutThisOP•

Thanks for the reply. I have an appointment at the dealer scheduled.

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mbait•

Any updates from the author? What was our take away from the service?

1
BetterWithoutThisOP•

Still in for service. They found plastic debris in the transmission fluid of unknown origin. TCM has been replaced, transmission flush and fill performed, Volt still not performing correctly. Per GM advice, they are replacing another part which they claim is redesigned. Just woke up, I can't remember what part that was. Something else transmission related.

2