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Discussion Starter #1 (Edited)
First of all a big thank you to everyone on this forum. There’s a lot of misconceptions and misinformation about this vehicle and it's nice to have a thorough source for facts, opinions and information on this great car.

A couple weeks ago I joined the ranks and purchased a ’17 Premier. Thus far I’ve been really impressed with the driving experience, the technology, how seamlessly the system operates and most of all the efficiency. Unfortunately GM’s quality control on it is less than stellar. My Volt is currently in service for the second time in less than week.

I was driving on the highway to the office on electric power (normal mode) using adaptive cruise when it suddenly disengaged and the car chimed for me to take control of the accelerator. Then immediately the check engine light came on. There wasn’t any jolt, loss or power or any other issues—the car continued to drive normally. Given that, being very close to work and running late, I let it go until later when I had free moment. I powered the car on again and the light was still there so I had OnStar run a diagnostic and it came back with a P25C9 transmission brake control code. The more detailed explanation for the code is that there is an issue in the fuel management system used to maintain and control fuel consumption. I was then told by OnStar it was wasn’t something that would endanger me or leave me stranded, but it is recommend I bring it into service within seven days. Due to work obligations I put that off until two days later when I could make arrangements and book an appointment. In that time the error code had cleared itself, but I brought it into the dealership anyway and I was told their diagnostics showed the issue was with the brake control module and it was reprogrammed.

I drove trouble free for the next handful of days and on my way home late yesterday evening driving on the highway in electric using adaptive cruise it again suddenly disengaged, the car chimed for me to take control of the accelerator and then check engine light came on. The same sequence of events as last time. I called OnStar again and after a diagnostic was run I was told the error detected was a P25C9 transmission brake control code. I asked if it was the same error, as I was driving and couldn’t safely pull over to check my records and found out they weren’t sure because once a vehicle is brought in for service or after 60 days OnStar clears its records. I digress but in an age of cheap data this sounds preposterous short sighted as that kind of info. could be invaluable if you’re running into an intermittent or difficult to diagnose problem. I then asked if there were any service advisories, bulletins or recalls on my vehicle and I was told one was issued that day under 2016017 battery cable misaligned. It was explained to me that 2016017 calls for the technician performing service at the dealer to check the cable and the fuse box to ensure it's properly aligned as it could be causing shortages and electrical arcing.

Given that the first check engine light automagically resolved itself by turning off before I got it to the dealer for service and that both it and this new check engine light occurred when running on electric power in the same situation and that the dealer servicing the brake pedal control module didn’t resolve the matter, my guess would be that the battery cable misalignment could be the true culprit, but I’m not a technician so I could be way off.

If anyone has any experience, insider knowledge or expertise on this mysterious problem it would be greatly appreciated.

When I picked-up my Volt a couple weeks ago I was confident I made the correct choice and selected the best vehicle for my needs and best plug-in on the market, but after receiving two check engine lights in a week’s time my confidence in both GM’s quality assurance on this vehicle and its dealer network’s ability to service it are pretty low and I’m beginning to question my purchasing decision.
 

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Thanks for the insight Steverino. Those shift to park warning sound terrifying. I'm glad to hear that thus far we haven't heard of anybody being injured as a result. My problem doesn't sound anywhere close to as severe as those given that my car operated as normal aside from the check engine light.

That battery tab bulletin from the linked thread is interesting. This car is technological marvel and so it's both surprising and unsurprising that something as simple a crooked tab can potentially cause so many troubling issues. The text describing what to look out for has some similaraties to what the OnStar rep. described, but I was told this cable misalignment advisory/bulletin/recall (I was never told exactly which of these it is) was brand new as of yesterday. The dealer hadn't herd of it until I mentioned. In fact I was told it's so new they don't even have procedure ready on how to address it. That befuddles me. Unless it could be potentially life threatening why issue a warning until you're able to properly address and resolve the issue.

Lastly, a small update. My dealer told me the cars warning codes and the communications with the techs at GM point to brake control module again. They were asked to reprogram it but they mentioned they already had previously and with the latest software so they are going to replace the part instead. This isn't a part they have in stock but it has been ordered and should be on track to arrive tomorrow. I'll update again when the part has arrived and been installed.
 

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Discussion Starter #4
I got my car back. As per the previous post the brake pedal position sensor was replaced and the codes were cleared. Hopefully this resloves the check engine light issues for good—fingers crossed.
 
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