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Discussion Starter #1
I've never had an issue charging prior to today... just hit 103K miles so no warranty.

At work I have a 240v outlet. When I went out for lunch the car was fully charged to 41 miles and ran normally in EV mode. As i was heading down the road the dreaded "Service High Voltage Sytem" alarm came on, but the car kept running fine. The car has had the WOT coolant fooler on for 5-6 months with no issues. Coolant is full.

When I returned from lunch and plugged the car in it would not charge; just the yellow light and "unable to charge" message. It was about then I noticed that a plant electrician had been working on the lighting circuit in this parking area. I went and asked him to help me out; we tested the receptacle and everything was fine. The EVSE was showing power and "charging" was lit. The 12v battery read 13volts with the car off.

He did admit that he may have shut down one leg of the 240v with the work he was doing... would that be enough to trigger these CEL codes?



Never could get it to charge, so I gassed my way home; it would not charge at home either.

I used the Torque Pro app and my ELM327 adapter to clear these codes and now she is charging away happily.

As I understand it P1E00 is a generic electrical issue code

P0AA6 is listed as a "Historic Fault"
P1FFF is also "Historic Fault"

We just returned from the longest gas trip we have ever taken in a Volt- would this have any bearing on the issue? I checked the oil and coolant levels at least twice a day at gas stops.
 

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Discussion Starter #3
The 12v battery is the original from a build date in 2012.

It may be time to replace it.
 

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These codes are normally caused by a low coolant level on the drive motor battery coolant system or a bad level sensor/wiring issue.
I have had a few cars that come in with a normal coolant level so I replaced the level sensor just to have the car come back in with in a few months. The repair made after the cars have some back was to rewire the coolant level sensor from the HPCM2 to the sensor, this by-passed a connector and also replaced the terminals on the HPCM2. The cars never came back after this this repair, not sure it this is going to be the issue on your car since you have the dummy sensor installed. Since you have cleared the codes and the system is now charging, go ahead and drive the car until you have this issue again before having any repairs made. This issue would not be caused by the charge cord or losing any voltage during charging or driving on a long trip. The codes are for a low coolant or loss of isolation on the high voltage system.
 

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I'm at 101,410mi as of now. I just had to replace the 12 battery after a lightning strike (to the local grid, while car was charging) took out the 12V systems. $300 for a battery, $3,400 total bill. The original 12V batt ran the car for 2 days on it's own and then would not accept a charge once the charging module was replaced. My advice is be proactive about replacing the 12V battery to avoid downtime since it is so critical for proper computer function..

Gotta love Torque!
 

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Discussion Starter #6
Full charge last night and again today at work.

I really appreciate your input mpmoore and Sir. Looking into getting a new battery and getting the coolant flush done.

Perhaps have them check to see if the car is missing any updates.
 

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I recently had the exact same problem. Like you, I also had the WOT defeat plug installed for months before the problem surfaced. This is very strange because it is exactly what the WOT defeat plug is supposed to address. That is to say that the OEM low coolant sensor creates a fault even when the actual fluid level is proper. Something else must be going on. I was not able to reset the fault codes using Torque and thus had to go to the dealer for a reprogram of HPCM2 and BECM modules. I reinstalled the original sensor. I am not sure what to do now. Will this problem resurface again, or not?
 

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Discussion Starter #8 (Edited)
Well, it seems to be triggering at the end of every charge session now. Two different EVSEs. Car still functions normally in every way.
I will be taking it in to see the local Volt Tech on Monday... first repair out of warranty. Hope it doesn't hurt too bad.
 

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Discussion Starter #9
How old is your 12v battery?
I put a new AGM from Advanced in about a week after you posted this; 5 years is good enough service from a battery.

This car has a low serial # for a 2013 last of the VIN is 03159. Makes me wonder if the early '13 models had wiring harness issues like the '11-'12s. .
 

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Discussion Starter #10
Update-

This is randomly triggering every few days now. It *has* now interrupted charging on 2 occasions.


Been running Torque Pro monitoring voltages and a few other things, but I'm not seeing anything that correlates with the fault being set. I have not had time to get it into the dealer. Being out of warranty a visit to the "Volt" techs we have locally makes me nervous. (There is some previous history with 3 GM dealerships for warranty issues) I don't mind paying top dollar for a top notch tech, but I hate paying top dollar and having my time wasted with several return trips and the associated hassle it brings. None of the local dealers have inspired confidence.
 

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Discussion Starter #11
GDS2 screenshots

Decided to see if I could delve a bit further into this SHVCS error on my own. Attached a VCX Nano and used GDS2 to take a look.


SHVCS.jpg

As you can see the typical pattern for this problem.

Why did GM combine the coolant level sensor with the High Voltage Isolation test??? :confused: :confused: Makes no sense.
 

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Discussion Starter #12
Are isolation resisitances ok??

HybridPackResst.JPG

Isolationres1.JPG




Ran the High Voltage Isolation Test and this was the result:

HighVoltageSysPassed.jpg


Does this mean I can rule out the isolation resistance and start looking into the WOT sensor or wiring to the sensor??


I didn't have as much time as I would have liked to delve further into this and I may not for a few weeks as I will be away from the car for a time. Curious what kind of input I can get from the experts here on the forum.
 

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I can tell you from experience if you are using an L2 Charger and it drops a leg it will throw those codes. They are clearable with any obd2 scanner.

GM went overboard with the fault codes after some of the volt fires. Then they loosened up and allowed an later firmware reflash ( which combined with the faulty coolant sensor ) is why so many are having this problem to allow more resistance as many many cars aged started throwing the SHVCS from a couple hundred ohms of resistance.
 

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Discussion Starter #15
I can tell you from experience if you are using an L2 Charger and it drops a leg it will throw those codes. They are clearable with any obd2 scanner.

GM went overboard with the fault codes after some of the volt fires. Then they loosened up and allowed an later firmware reflash ( which combined with the faulty coolant sensor ) is why so many are having this problem to allow more resistance as many many cars aged started throwing the SHVCS from a couple hundred ohms of resistance.
Interesting. I'm convinced you are right. Wasn't it just one fire, though?? Started after a crash test and while hanging in an unnatural position??

I've been out of town for a while. As soon as I get a few days off I will see if I can do the HPCM2 and BECM updates via the GM subscription program. I just don't have time to mess with the dealership right now.

Surprised at the lack of interest in this. Maybe as more people go over the 100k warranty period it will help someone out.
 

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Discussion Starter #16
Success!!! (I hope)

Today I was able to get connected to the ACDelco TDS system and reprogrammed the HPCM2 and BECM to the latest and greatest. Acess to GM's system programmer was $55 for 2 days. Only took me about 1 hour to get it done. For a J2534 device I used the VCX Nano and the great guide by CCIE(a member here) that can be found in the WOT coolant temp sensor thread. Big thanks to CCIE!! :) :cool:



















So it is possible to get this annoyance fixed without a dealer visit. And now I have a tool that can be used on both my Volts to diagnose and repair/replace parts when needed. Thanks to all here that have contributed and made this possible.
 

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As I understand it P1E00 is a generic electrical issue code

P0AA6 is listed as a "Historic Fault"
P1FFF is also "Historic Fault"
How did this turn out for you. I have the same issues in my 2012. Replaced the sensor but codes come back within a few drives.
 
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