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Discussion Starter · #1 ·
Hi all,
Been dealing with a high voltage error code in my 2013 Volt for a few months. I'm sure many of you know the experience of high voltage system unavailable and the high ICE revving that comes along with it, so I don't need to describe that. I'll try to summarize my issues and go from there.

It's always come up after charging, it either stopped charging partway through or it finished charging but I didn't know it...

First time it came on was a saturday, the following day everything was normal besides the CEL staying on for a few days. I was busy and didn't have time to go to the dealer, so I let it be. That only lasted a week or so...

2nd time was also a Saturday. Still busy, but I did finally remember to call into service and make an appointment during the following week. Got an appointment a few weeks later, problem recurred several times while waiting for the appointment but was usually gone the next time I drove it. They did the battery balancing update programming and things seemed fine. I also had them do my 5 year coolant flush at that time.

A few weeks later, seemed like the problem was gone... nope! Back again. Same code, same pattern of working again the following day. Scheduled an appointment and they replaced the charge port and charger itself. That was two weeks ago...

Today it happened again. P0AF8. Based on previous experiences I sat in the driveway letting the ICE run for a few minutes, then turned the car off. Waited a minute, turned it back on and I had battery power again! I started my drive and the GOM went from 11 miles up to 29 as I was getting down my street. About a mile later, while I was driving it switched over to crazy-ICE mode and revved it's way to our destination. Came out an hour later and it was electric all the way home (although only estimating 13 miles).

So... back again. Based on my searching on this subject, and the way my GOM changes wildly at times, I'm guessing I have a bad battery cell in the main drive battery. Any other possibilities? Does it seem like the dealer hasn't done their testing properly? I was hoping they would flag a bad main battery cell if that were the problem, considering the number of times I've been there recently.

I suppose it COULD be the 12V battery, but I've no other symptoms to indicate this. I had the 12V battery tested recently and it passed load testing and reported healthy, but it is still the original 12V battery. I forget how many CCA they rated it for, but it was well within spec.
 

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sure you already know this but for others reading

High voltage system may not operate Symptoms

High voltage system may not operate

Vehicle will not charge

Common Problems That Trigger the P0AF8 Code

Auxiliary 12V battery failure
Battery Energy Control Module (BECM) failure
High voltage battery assembly failure
 

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Discussion Starter · #3 ·
I scheduled an appointment at the dealer for tomorrow, will find out more then. The way it's working right now, if I don't plug in anywhere, it runs fine in normal 'hybrid' mode. If I plug in to charge, it will disable the high voltage system for the next drive, and go back to normal the following drive. So pretty much I can't charge.

Considering they replaced the onboard charger a couple weeks ago, I'm assuming there is some sort of problem with the new one... how can I be sure they are doing a full diagnosis? I want to make sure they aren't just randomly throwing parts at it. I'm not sure how much faith I have in my dealer's tech. I'm tempted to try another dealer, but the inconvenience of the next closes dealer's location is a holdup for me.
 

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I scheduled an appointment at the dealer for tomorrow, will find out more then. The way it's working right now, if I don't plug in anywhere, it runs fine in normal 'hybrid' mode. If I plug in to charge, it will disable the high voltage system for the next drive, and go back to normal the following drive. So pretty much I can't charge.

Considering they replaced the onboard charger a couple weeks ago, I'm assuming there is some sort of problem with the new one... how can I be sure they are doing a full diagnosis? I want to make sure they aren't just randomly throwing parts at it. I'm not sure how much faith I have in my dealer's tech. I'm tempted to try another dealer, but the inconvenience of the next closes dealer's location is a holdup for me.
What did you ever figure out with the P0AF8 code? I am having the exact situation you were having. Error only when charging
 

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Discussion Starter · #5 ·
What did you ever figure out with the P0AF8 code? I am having the exact situation you were having. Error only when charging
The dealer replaced a big module. I know it would have been expensive but I don’t remember the name of it. It was two years ago so I’ll be lucky to find the paperwork but I’ll take a look.
 

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The dealer replaced a big module. I know it would have been expensive but I don’t remember the name of it. It was two years ago so I’ll be lucky to find the paperwork but I’ll take a look.
Hi i have the same issue please deekster_caddy can you share the part that was replaced.
 

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The dealer replaced a big module. I know it would have been expensive but I don’t remember the name of it. It was two years ago so I’ll be lucky to find the paperwork but I’ll take a look.
Hi i have the same issue please deekster_caddy can you share the part that was replaced.

car not charging p0af8
1) changed the 12 v battery
2) updates all battery related computer modules to latest version
3) changed the charging port

now i am wondering if its the on board charger module in the front passenger side of the volt or the contactoe assembly on the battery pack it self
 

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Back to square 1

changed the on board car charger( behind front right side bumper) flashed/programmed every electronic module.
It worked for a few charges and stopped again then out of the blue started charging again after a few days again not charging.

now its giving thr same code again p0af8
 

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Cheers man, I feel your pain. Also been dealing with P0AF8 for years. Two replaced charge ports but still comes back. Seems to spontaneously occur and resolve. Taking it in for another look on Tuesday. Will report back with findings. Curious if you have any updates?

Back to square 1

changed the on board car charger( behind front right side bumper) flashed/programmed every electronic module.
It worked for a few charges and stopped again then out of the blue started charging again after a few days again not charging.

now its giving thr same code again p0af8
 

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Cheers man, I feel your pain. Also been dealing with P0AF8 for years. Two replaced charge ports but still comes back. Seems to spontaneously occur and resolve. Taking it in for another look on Tuesday. Will report back with findings. Curious if you have any updates?
Anxiously waiting for your results. For my volt I am thinking that i may need to drop the battery and change the contractors assembly that is in front of the battery.
 

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The code mentioned appears to be a battery balance issue. Have you checked the individual cell voltages (i.e. MGV app)?
 

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The code mentioned appears to be a battery balance issue. Have you checked the individual cell voltages (i.e. MGV app)?
I will check the individual cell voltage. I have attached the repair instructions from "Chilton online" for P0AF8 that I have been using.

I looked at the voltage when it was fully drained and all cells were the same voltage. Just yesterday I was able to charge it and I will check again the individual cell voltage in fully charged state add screenshots.

:)
 

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I have been using VxDiag for this. I dont have android phone for the MyGreenVolt App... I will post screenshot ASAP :) Thank you for everyone's prompt replies.
 

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Hi Everyone, I hooked up to the car and took screen shots of the

I can get more screenshots of any data points that may help.

All 3 coolant bottles (engine, charger, battery) are to the full mark.
 

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"Battery Energy Control Module (FULLY CHARGED STATE ) All cells from 1 - 96 are holding around 4.04 and some are going from 4.03 to 4.05.
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",
 

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"Hybrid Powertrain Control Module 2 (Voltage Data, Temperature Data, Contactor open reason, Contactor data, Charge History )
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