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I have a 2012 Gen1 Chevrolet Volt purchased new in 2013 with 125,000 miles on it. I have received the SVHVCS message several times and have always reset with a standard OBD scanner. My battery coolant has never been replaced and I am running the coolant at the new level but have never had to add any since it was increased to the new level. It is also interesting that the SVHVCS error has typically never occurred in the winter when it is cold.

In April I got the dreaded P0AFA and P1E00 error codes. The car was in my garage at home with no way to get it out.

My car still had the original 12V battery, so the first thing I did was went to my dealer to get a new battery. They had to order one so I had to wait a week to get. Just as a reminder if you take the battery out, don't close the trunk. I couldn't find a way to release the trunk after I removed the battery, so had to crawl in from the rear seats to finish the battery replacement.

The battery replacement didn't fix the problem and the dealer told me it would be two weeks before they could look at, so rather that having it towed in and wait, I decided to do some reading. I ended up ordering a VXDIAG VCX Nano and paid the AC-Delco subscription cost and reprogrammed the Hybrid Powertrain Control Module 2 with the SPS tool and then cleared the DTC's using that tool and all was working again. I charged the vehicle up and drove it for two days and the error code came back again. I reset the code again and decided to keep my dealer appointment. After convincing them to charge and drive it around a little the error came back. They diagnosed and indicated that there were bad cells in every section and therefore I needed a full battery replacement. Initial estimate was $10,000 for the battery and labor.

I decided to try the Mountain Mode idea mentioned by others, so drove around for a few days in mountain mode and charging when I got home making sure I had a laptop with me. As long as I have an Internet connection, it takes about 8-10 minutes to plug in start the software reprogram the HPCM2 module and the clear the DTC's. This is still a little too scary to continue doing long term. My initial analysis is that is that mountain mode is not the answer since I was still getting the P0AFA code occasionally. When everything works, I am getting about 9 kwh usage from the battery and about 30 miles of range so it seems like the battery isn't close enough to being dead that it should really need to be replaced.

After several different tests and resets, it appears that the P0AFA error code is primarily happening when the car is charging or while it is sitting still in a parking lot. As an example, I have driven to work and when I get to work turn the car off and on several times to be sure the error is not present. When I return to the car in the afternoon the error code is present and I have to pull out the laptop to reset.

I am still unable to convince myself that my only options are to either trade in the car (Best offer so far is $2,500 for trade.) or replace the battery. Surely there is a way to operate the battery with a greatly reduced range/capacity and use the ICE, but I haven't found any successful solution so far.

I have just downloaded MyGreenVoltConnect and MyVoltControl to see if there are any more insights I can gain from these. Maybe if I used the hold mode from one of these keeping the battery at a higher state of charge it might work?

My next thought is to take it to the dealership and have them replace the battery coolant as it really seems this is part of the problem, but I don't want to keep dumping money into the pit.

Anyway, I thought I would see if anyone had other thoughts / suggestions.

Here are a few of the screen shots from the Apps that I took a few minutes ago with the car charging.

Motor vehicle Font Technology Automotive exterior Electronic device

Font Rectangle Parallel Grass Pattern

Black Goggles Speedometer Gauge Sunglasses
 

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OpenEVSE home charger, 2013 Volt base, added tow hitch, K&N filters, 3d printed interior mods, etc
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What's the balance look like at the low end of SOC, right when it switches to CS mode on it's own?
 
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