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2012 Service High Voltage Charging System with WOT's Sensor Defeat Plug in place ????

29866 Views 55 Replies 23 Participants Last post by  Rollmann
Kudos to WOT for developing his battery coolant level reservoir sensor replacement/defeat plug. This device essentially mimics the electrical characteristics of a properly functioning OEM coolant reservoir sensor. The stock/OEM sensor is a cheap and flakydevice that can and does fail, causing the setting of fault codes that require dealer level tools to clear the codes.

My early 2012 developed the Service High Voltage Charging System error message months after having installed the WOT sensor replacement. This occurred after a successful recharge while still connected. I scanned for the DTC fault codes with a tablet running the Torque app. Initially the codes were B2AAA, P0AA6, P003E, P1FFF, P1FFF. I tried to clear the codes with the Torque app but as WOT has previously posted only dealer level tools can clear all these codes. The clearing process is in fact a reflashing of the software for the HPCM2 module. After my attempt at code clearing another scan reported P0AA6, P1E00, P1FFF.

I could not charge the battery with either my L2 charger or the stock L1. I uninstalled the WOT defeat plug and reinstalled the original stock sensor prior to bringing the Volt to my original new selling dealer service department. All recalls and servicing have been performed by this dealership. The dealer's diagnosis/repair efforts stopped at square one when they discovered that their Fluke 1587 multimeter was missing and was a required tool in the GM diagnostic procedure. Surprising to me was that the next closest Chevrolet Volt dealer also did not have the required instrument. I guess this is a reflection of how few Volts they service. I had to travel to a dealer a hour away who had the required tool.

I was thinking that there must be some real failure, separate from the reservoir coolant sensor issue, that was casing the faults. Possibly a harness issue as a result of poor workmanship when the battery compartment structural enhancement recall was done a couple of years ago. I had asked the dealer service writer to have the tech perform a reflash of the HPCM2 and Battery Energy Control Module to clear the latching error codes as a first step to see if the faults would then reappear. They refused saying that they needed to follow the documented GM diagnostic protocol steps.

They called a day later to report the Volt was now repaired with nothing other than module reprogramming. The notes on the invoice are:
"Scanned for P0AA6 and P1FFF. Isolation test resistance 250K. Bulletin PIC59206 requires to check coolant level, check moisture in battery as well inspect plugs. No issues found. 2880268 reprogram HPCM2 and BECM"
"The HPCM2 is up to date but not BECM. Programmed BECM and tested resistance. Now at correct specs 3000K. All OK at this time. Programmed CD0D3."

I am glad the Service High Voltage Charging System error message is now gone and I will be able to recharge the battery. But, all of the above is a bit baffling to me. With the WOT coolant sensor defeat plug in place for months without issue and the coolant level at the revised proper level, what triggered the error codes? How could reflashing/reprograming the HPCM2 and BECM cause the isolation resistance measured with the Fluke 1587 multimeter to change form an apparently to low 250K to a proper 3000K? This sound illogical to me. And what is the CD0D3 that was reprogrammed, and what does it have to do with the fault? I cannot find anything about the CD0D3.

Should I know reinstall the WOT sensor coolant defeat plug or leave the apparently correctly functioning coolant reservoir sensor in place?

WOT, if you see this post I would appreciate your take on this and guidance.
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If it was my car having the issue and I was to install the defeat sensor, I would wire it next to the HPCM2. You would have to splice in to the harness but its not that hard. The HPCM2 is just in front of the front passengers seat under the carpet, there is a cut out in the carpet to get to the HPCM2 so you do not need to remove the carpet to get to the module.
@mpmoore1979 I live in Honduras and have zero dealer support here. My Volt has the "Service High Voltage Charging System" with WOTs defeat plug installed. I already flashed the HPCM2 once with the aid of a VCX Nano, was able to delete the latched codes and charge the car, following these instructions: http://gm-volt.com/forum/showthread...ing-System-quot-Message&p=4153377#post4153377

Nevertheless, the "Service High Voltage Charging System" DTCs are back. I would like to try installing the defeat sensor next to the NPCM2 to rule out harness issues, but I'm having trouble identifying the correct PINs. I have the Service Manual and believe is PIN 25 of K114B Connector 2X1 (Rechargeable Energy Storage System Coolant HVAC Mode Sensor Signal). This is the only descriptions that seems to match this sensor, but it could be that my manual was printed before the Coolant level sensor recall was issued and it simply doesn't include reference to the PIN where this sensor goes to.

I will be very grateful if you can assist me in identifying the correct PINs to install the defeat plug. I haven't been able to enjoy my car for 6 months now.

Thanks
 

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Codes are: P0AA6, P1FFF and P1E00. In my case the coolant hasn't dropped, I have WOTs defeat plug, so I decided not to perform all the diagnostics in Service Bulletin # PI0961C and assumed the most obvious, a problem with the harness.

Anyways, I would like to install the bypass next to the HPCM2 (K114B) to avoid the extra variables of the harness. Anyone knows the PINs?

Thanks
 

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They called a day later to report the Volt was now repaired with nothing other than module reprogramming. The notes on the invoice are:
"Scanned for P0AA6 and P1FFF. Isolation test resistance 250K. Bulletin PIC59206 requires to check coolant level, check moisture in battery as well inspect plugs. No issues found. 2880268 reprogram HPCM2 and BECM"
"The HPCM2 is up to date but not BECM. Programmed BECM and tested resistance. Now at correct specs 3000K. All OK at this time. Programmed CD0D3."

I am glad the Service High Voltage Charging System error message is now gone and I will be able to recharge the battery. But, all of the above is a bit baffling to me. With the WOT coolant sensor defeat plug in place for months without issue and the coolant level at the revised proper level, what triggered the error codes? How could reflashing/reprograming the HPCM2 and BECM cause the isolation resistance measured with the Fluke 1587 multimeter to change form an apparently to low 250K to a proper 3000K? This sound illogical to me.
The isolation test resistance using GDS2 diagnostics shows 225 kOhm. Could it be that my problem is also BECM not up to date?
HPCM2 Data Screenshot:

Text Line Font Parallel Document


I would still like to install the defeat plug next to the HPCM2 to avoid harness issues, but I can't seem to find schematics to show PINs in the connector to hook up to. Tomorrow I'll try to follow the lines from the coolant sensor to the HPCM2 and figure this out on my own since I've been waiting for weeks here for some feedback with no luck.

This is the Battery Charger Module Data:

Text Font Line Screenshot Document
 

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Fixed by hosting image elsewhere.

Do you know if the "Isolation Test Resistance" shown in my report is equivalent to your "Hybrid/EV Battery Pack Resistance"?
 

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I’ve been driving on gas for over 6 months now. Still haven’t fixed this issue. Tried to follow the cables from the sensor but they merge with a bunch of cables making it a daunting job.
Haven’t had time for other options like looking at cable color codes or checking continuity. Also checked the shop repair manual with no luck.
Will post PIN info whenever I get it done since it seems nobody has done it before or shared it.
 

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I found part of schematics on German forum it can be seen that connection is on X1 32 33. If I am correct 33 is ground, you can check on conenctor at sensor if ground is ok. here: .opel-ampera-forum.de/viewtopic.php?f=34&t=1830&hilit=f%C3%BCllstand&start=230
I am not able to post image or whole link as i am new here. just add triple w before
Let us know how it goes.
Thank you. Here it is for anyone that finds it useful:

Text Floor plan Diagram Circuit component Line


 

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I found on German forum that there should be 5V on sensor. You can measure that as first thing, so you can se if harness is ok. On page 36 of the forum thread I sent before, you even have instructions that you can redoo what was originally done when sensor was added. as I can see, sensors were faulty because of bad soldering inside of them, so having a spare one instead of just WOT resistor is not bad and price is low. And newer should be without this bad soldering fault. Some reported of dead HPCM2, but this would probably make car dead.
Will give it a try on the weekend and report back. I appreciate your assistance, specially because I have no dealer to go to, my Volt is the only one in the entire country, only EV actually. I have PV system and got myself the Volt so I could charge it with solar power, but haven't been able due to this problem.

Here is the larger schematic:

[iurl="http://gm-volt.com/forum/attachment.php?attachmentid=145994&stc=1&d=1516141763"]
[/iurl]

 

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I found part of schematics on German forum it can be seen that connection is on X1 32 33. If I am correct 33 is ground, you can check on conenctor at sensor if ground is ok. here: .opel-ampera-forum.de/viewtopic.php?f=34&t=1830&hilit=f%C3%BCllstand&start=230
I am not able to post image or whole link as i am new here. just add triple w before
Let us know how it goes.
I'm checkin the Service Manual for 2012 Volt, HPCM X1 connector, PIN 32 is labeled AC Refrigerant High Temperature Sensor Signal, circuit 732, Color: WH/L-BU and PIN 33 is labeled Low Reference, circuit 452, Color: BK/VT. According to diagram you shared, PIN 32 is circuit 68, Color: L-BU/YE and PIN 33 is circuit 476, Color: BK/L-GN. It might be possible it corresponds to a different year model or Ampera has a different schematics. Nevertheless, I'll try to verify correct PINs during the weekend.

Again thanks for your help.
 

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Just wanted to report I got it done over the weekend. I updated the Battery Energy Control Module as reported by OP and the latched DTCs didn't come back. Guess an updated Hybrid Powertrain Control Module 2 (HPCM2) without updating the BECM results in a conflict issuing the latched Service High Voltage Charging System DTCs.

Since I had paid for the ACDelco subscription I went ahead and updated other modules as well: Battery Charger Control Module, Body Control Module, Coolant Heater Control Module, Engine Control Module and Electric Power Steering Control Module.

Will write up everything at a later date for others to benefit from my research and experience solving this issue.

Thanks for everyone that helped.
 

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Good news, now there's a two year subscription for Vehicle Programming Software. It includes: 24 months access to program all modules for one vehicle (VIN) for $40. Too bad this wasn't available when I did mine, I even had to pay twice since I didn't get it the first time ($55 x 2).
 

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One thing I noticed however, was that when I was done the reprograms, the main dash said 'service theft deterrent system' before I took the car out of service mode. Once out of service mode, the main dash did not show any messages. I saw the 'service theft deterrent system' message after each re-programming, because I took it out of service mode and powered up normally in between them.

Has anyone seen this message before? Some quick searches have shown that a degrading 12V battery could cause this, so I'm thinking about replacing that out of caution. I bought the car used and have had it for two years, so it wouldn't surprise me if it's starting to degrade.

Thanks.
I had the Service Theft Deterrent System alert and it was caused by a weak ground connection. You can find details here to compare to your symptoms:

https://gm-volt.com/forum/showthread.php?257233-Service-Theft-Deterrent-System
 
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