2012 Chevrolet Volt Service High Voltage Charging System

Wayne Owner/Technician Ontario Posted   Latest   Edited  
Unsolved
Electrical
Electrification
2012 Chevrolet Volt 1.4L (4 LUU) (4ET50) — 1G1RA6E42CU104224
P0AA6-00
P0CD2-00
P1EC6-00
Intermittent Service High Votage System

Good morning All,

This Volt came in about 2 weeks ago after being at the dealer with only codes P0AA6:00 System isolation lost and P1FFF:00 coolant level sensor fault charging system disabled. The customer was estimated to START with a battery installed north of 15K (CAN). The vehicle was purchased only a few months ago used and at that repair cost, well the economics just don't work out for him. I wanted to get a look at it myself as I was interested in the coolant level fault possibly being the culprit and have a specific question about this.

I brought the vehicle in, checked the battery isolation resistance and it is within spec (VIA resistance PID). Checked cell voltages and all good. I checked all the module software and noticed that only the HPCM modules had the newest revisions. I took some time to update all modules including the external charger.

Once this was all done I kicked it out the door with a clean slate to see what would happen. All was good for about 3-4 days and 120km later the check engine light came on and Service High voltage charging system came on. I got it in quickly and checked for codes again. Both P0AA6 and P1FFF were set at the same time, no other codes. There is no coolant level sensor PID in any of the modules, still can't find it anywhere so I hooked up a graphing meter to it and drove it for about 45 min and output voltage was within spec and didn't waiver. Easy to replace, low cost, figured wouldn't hurt to throw a new one in and let it out into the wild again after a reflash. Only way to clear codes in this vehicle is a flash FYI.

4 days it performed perfectly until yesterday, CEL and Service High voltage at about 150km of driving.

Codes this time were the same with two new ones for the charge port and battery pack heater performance. There is a TSB for the microswitch in the charge port but I really would like to get this low coolant issue straightened out first.

My question is. Does a level sensor trouble code always have a P0AA6 isolation lost code. What I am trying to say is system isolation lost ASSUMED because of the low coolant trouble code. It seems weird to me there would be a isolation problem at the exact same time as a low coolant warning. Isolation resistance on the scan tool has never dipped below 565kohms and I am wondering if the logic is such low coolant assumes a possibility of no coolant and just shuts the HV down for safety. I can make the call on a new battery but not until I see system isolation lost without the low coolant trouble code.

FYI, this has the revised coolant bottle with the locking cap AND there was never a loss of coolant, no moisture in the drain plug battery tray hole.

ALL modules updated

new coolant sensor AND pigtail

The costs of repairing these vehicles is stunning and I can't believe this is not part of any media vernacular. Maybe because its being discouraged to shed negative light on greenish vehicles but considering the billions of dollars and chronological promises our leadership is making this is a game changer for this industry. I come from a time where electronic ignition was being poo pooed by older techs and cut my teeth as an apprentice on lean-burn HEI and TFI systems. The real concern is the general motoring public that can afford vehicles at a price point they are beginning to fail is going to be financially crushing to them.

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Interesting
Nick Diagnostician
Missouri
Nick
 

Make sure the electric water pump near crank pulleybis working. Their is updates avaliable for the isolation fault codes and the only way to clear them is flash the module. Inwant to saying even states that in a tsb or si

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Wayne Owner/Technician
Ontario
Wayne
 

yes its working I mentioned in the post I know it has to be flashed to clear codes.

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Nick Diagnostician
Missouri
Nick
 

Sorry was driving and only skimmed through post before responding

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Wayne Owner/Technician
Ontario
Wayne
 

Lol that is me reading 99 percent of what is sent to me! No worries, thanks for the input!

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John Educator
Utah
John
   

Isolation resistance anywhere near 256k ohms is a problem. 3000k ohm is a normal reading. The battery isolation resistance is checked after the car is shut off and the contactors have opened. When you say “new coolant sensor AND pigtail,” did your new pigtail replace the pigtail installed as a result of the 2012 recall? There is no PID because that harness used to be an A/C pressure switch. The…

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Wayne Owner/Technician
Ontario
Wayne
 

I installed a new pigtail because I did not catch any faults when driving and wanted to make sure the sensor itself and connection was good in one shot.

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John Educator
Utah
John
 

I understand that, but that is not what I am asking. The original recall in 2012 had a technician install a pigtail with two crimp and seal connectors. Did your new pigtail replace the original pigtail? in other words, are the original crimps from the first pigtail still in the harness?

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Wayne Owner/Technician
Ontario
Wayne
   

My post has a typo it should say 565k not 265k ohms. I am going to check the pigtail issue today (I ordered them both from GM and assumed they are a match) and get it back in and see the PID for isolation resistance again. This raises an interesting question though, it says in the service manual : Observe the scan tool hybrid powertrain control module 2, Isolation Test Resistance parameter. The…

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Matt Owner/Technician
Ohio
Matt
 

I have experienced this symptom as well. First and foremost most make sure all the latest calibrations are loaded, which it sounds like you already did. The next suspect is likely the HV coolant heating element inside the battery pack. I have replaced a couple of these. It is inside the battery and requires dropping the battery to access, not terribly difficult to do. This heating element uses…

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Matt Technician
Massachusetts
Matt
   

Hi Wayne, I've delt with this same issue on the … Volts a few times. To your questions “Does a level sensor trouble code always have a P0AA6 isolation lost code.” The P1FFF is a very strange code. It's basically has a dual meaning. The code description mentions both a HV Battery coolant level issue as well a loss of high voltage isolation. It's fair to say that a leak in the HV…

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Stuart Owner/Technician
Minnesota
Stuart
 

I might be that other shop owner Matt mentioned! I totally agree that GM seems to have told the software team to freeze development one day and left a bunch of threads hanging. It is a mess but it is what it is… GM states that P1FFF is an “umbrella code” and it has no actual definition. They recommend pursuing the other code(s) that comes with it. I did have this code solo, so for testing…

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