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Keep in mind, they will probably end up having to reprogram HPCM2 again, AFTER replacing the coolant level sensor. An undocumented "feature" is that the HPCM2 monitors the coolant level for 10 minutes AFTER the ignition is OFF or CONTINUALLY during active charging.
So replacing it without triggering the entire mess of DTCs again is a bit tricky. You must leave the car OFF with the hood open for 11+ minutes before changing the sensor, which is easy as it simply "pops" out of a small receptacle on the bottom of the reservoir.

HTH
WOT

WOT, could us regular folks just not clear the latched DTC fault with a cheap ODB-II tool or does this actually require a full program performed by the GM service dept? I take it this level sensor can be changed w/o draining or re-filling the 50/50 Dex-Cool. It would be cool if you could take a pic of your bypass. Does it create an open or short in order to 'fool' the HPCM2?
 

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WOT, could us regular folks just not clear the latched DTC fault with a cheap ODB-II tool or does this actually require a full program performed by the GM service dept? I take it this level sensor can be changed w/o draining or re-filling the 50/50 Dex-Cool. It would be cool if you could take a pic of your bypass. Does it create an open or short in order to 'fool' the HPCM2?
Unfortunately not somms. Wouldn't that be nice. Even the GM OEM equipment (GDS2/MDI) cannot clear this latched situation through a simple clear DTC command. In fact, for whatever reason this is even more "locked up" than the "secured High-Voltage DTCs" that must be cleared in HPCM1 and 2 via specific control functions in GDS2. (not aware of an aftermarket tool that can do this either)

The frustrating part is how HPCM2 continually monitors the sensor even when OFF. So the DTCs keep triggering (in tandem with the LOI DTC) making the technician think there's something more wrong than a simple level sensor issue. Don't worry, I AM working with the GM SI authoring folks to get some changes made to the DTC documents. But the behavior itself is likely not destined to be changed at this point.

Take a look at the diagnostic steps for a P1FFF in an up-to-date Service Manual PDF ( assuming it's out there, an old 2011-12 that was released prior to the side-impact campaign won't cut it)
REPROGRAMMING HPCM2 (even if the identical files are being uploaded) is the only way to clear the P1FFx DTC/s and reset the SHVCS message.

WOT
 

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So my chevy dealer says my car is fixed. I'm going to pick it up. He says he only had to re-set the sensor and it was in a service bulletin 3 months ago. I asked if it was under battery warranty since it's part of the system. Of course he said no. I did have an oil change done too and the bill comes to $187.00 I guess I'll find out what I'm paying for when I get there. Is it likely I'll be back for the same issue?
 

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So my chevy dealer says my car is fixed. I'm going to pick it up. He says he only had to re-set the sensor and it was in a service bulletin 3 months ago. I asked if it was under battery warranty since it's part of the system. Of course he said no. I did have an oil change done too and the bill comes to $187.00 I guess I'll find out what I'm paying for when I get there. Is it likely I'll be back for the same issue?
If they didn't replace the sensor, you likely will be back.
There is no such "reset" process for the sensor, but unfortunately the level sensor fails intermittently.
I know of cars that have had 4 sensors in 2 years, and one 7 sensors in 4 years. (now of warranty the last "repair" was over $400!)
It may be high heat related.

WOT
 

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Here is the dealer diagnosis and reapir" Scanned system set code P1E00, POAA6, P1FFF Battery Voltage System Isolator System Isolation Coolant Level System Needs Updated Program INST 26 electrical repairs" 10866CP was the billing code for $135.00?? Wow no idea what all the system codes are. Does anyone have an idea?
 

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Here is the dealer diagnosis and reapir" Scanned system set code P1E00, POAA6, P1FFF Battery Voltage System Isolator System Isolation Coolant Level System Needs Updated Program INST 26 electrical repairs" 10866CP was the billing code for $135.00?? Wow no idea what all the system codes are. Does anyone have an idea?
Let's call that exact group of DTCs "Exhibit A" shall we? ;)
Don't sweat it. Refer to post #317 of this thread for the most effective advice we can give you.
http://gm-volt.com/forum/showthread...ing-System-quot-Message&p=3537746#post3537746

However we must recognize you are at the mercy of your dealer and YMMV

Good Luck!
WOT
 

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Thanks for the reference. That is great information. I wish I had read the bulletin you provided before I picked up my car and paid. I called a volt advisor from my car with onstar and asked them if my repair was under 100k warranty of Voltec system. They said it was and intervened with the dealer. The advisor said the dealer will be contacting me to refund money. I'm still concerned I will be doing this again soon but my car is working right now and accepting a charge.
 

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PS> I'm adding a PDF of the most recent bulletin regarding "low indicated battery coolant" however in my experience the issue is usually an intermittent battery coolant level sensor and while the bulletin promotes a thorough diagnostic routine that should eventually reach the root cause, it often leads to a lot of wasted time given the "known condition".
Thanks WOT, was interesting to see that bulletin. I've read and understand all your posts during and after my issue. Super appreciated!

In my case (a handful of posts previous) I had code P0AA6 along with P1FFF. And my dealer went off on a (presumably) red herring and dropped the battery on my Volt and replaced the Battery Coolant Heater blaming a shorted condition (though, they at first said open circuit....just all part of the confusion!). BUT, looking at that bulletin, it's hard to blame them. The very first page says if DTC P0AA6 is set then they're to go look at PIC5920A which is about Loss of Isolation. So I guess they did. I wonder if PIC5920A tells them to RETURN to the bulletin you posted so as to complete the advise in that bulletin to replace the Battery Coolant Sensor. My dealership clearly didn't....since I had to 'fight' with them to change the sensor.

I'd be curious to see PIC5920A if you felt like posting it. ;-)
Just all part of my gathering all pertinent data for when I (eventually) have to go back for the SHVCS for the fifth time (even though I did wrestle yet another new sensor from them in the end).

Hmmm, looking carefully at that bulletin you posted, I see a flaw. It lists the various DTC codes of P1FFB, P1FFC, P1FFD, P1FFE, and P1FFF. BUT....the diagnostic process they're told to follow on the second page (at Step 1) is silent about P1FFF! It says to go to Step 2 if the any of the first four DTC codes were set....but makes no mention of what to do if the DTC was the fifth (P1FFF). Doh! I suppose a dealership might reasonably conclude that they're to do nothing (ie. not replace the sensor) in the case of P1FFF....even though that would be an odd conclusion since P1FFF is listed as one of the originating DTCs. I guess if they saw P1FFF along with P0AA6 (as in my case) they'd branch to PIC5920A and even if they came back to this bulletin could reasonably concluded they shouldn't do the sensor since the sensor is only for the first four of five P1xxx codes. Clear as mud?

What a mess GM appears to have created on this whole topic with their own instructions to the dealership techs!
And painfully ironic since GM 'created' this sensor issue as part of the battery channel strengthening 'recall'....which came about at least in part due to the public's hysteria of that single spontaneous battery fire. Your comment earlier about how unnecessary the sensor is was enlightening illustrates how the sensor was overkill. I suppose GM is reluctant to take any formal corrective steps about the sensor because it would make them look rather bad after introducing the sensor with what was perhaps an inadequate amount of long term quality testing (ie. they rushed an overkill fix into place as a result of all the media attention).
 

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Would be interesting to see some pics of the sensor and explanation of the change out procedure if you have time.
Here you go
Finger Hand Thumb


As for removal, place your hand under the tank and locate the sensor. Once you've found it, lightly push it towards the front of the car and it simply slides out of place. Keep in mind as has been noted in this thread that this will trigger a code which only the dealer can clear.
 

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" Service High Voltage Charging System " Message

Here's a better picture of the culprit:

Green Technology Electronic device Plastic Electrical connector


GM's explanation can be found here:

http://media.gm.com/media/us/en/gm/news.detail.html/content/Pages/news/us/en/2012/Jan/0105_volt.html

Keep in mind as has been noted in this thread that this will trigger a code which only the dealer can clear.
Can't this code be cleared with an OBDII scanner?

I was advised that using a wireless scanner paired with an app like TORQUE PRO will clear this code. obdsoftware.net/software/obdfusion

Can anyone confirm if that's the case?
 

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Can't this code be cleared with an OBDII scanner?

I was advised that using a wireless scanner paired with an app like TORQUE PRO will clear this code. obdsoftware.net/software/obdfusion

Can anyone confirm if that's the case?
I have Torque free and the usual BT OBDII scanner. The code re-fires nearly instantly after clearing for me. I assume this was because I simply can't properly reset it. I haven't gotten my new sensor yet and perhaps my wires aren't fixed and that's why it's refiring, but I was under the impression this particular code required a reflash of one of the on-board modules.

Edit: It seems like it could be possible to remove and replace the sensor without issue if you wait 10 minutes after turning the car off. *** will have to confirm that though.
 

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Well I drove my car this morning on a short drive came home parked it in the garage and plugged it in. It wouldn't accept a charge. I unplugged it and tried starting it to drive it. Dash lights up, instruments function, but no starting noise it usually makes. When I put it in drive or reverse it will go nowhere with gas pedal depressed. Afterwards I can't turn off the car. Weird so I guess I'll get it towed to Chevy dealer on Monday. Any idea what's happening?
Let's call that exact group of DTCs "Exhibit A" shall we? ;)
Don't sweat it. Refer to post #317 of this thread for the most effective advice we can give you.
http://gm-volt.com/forum/showthread...ing-System-quot-Message&p=3537746#post3537746

However we must recognize you are at the mercy of your dealer and YMMV

Good Luck!
WOT
 

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Well I drove my car this morning on a short drive came home parked it in the garage and plugged it in. It wouldn't accept a charge. I unplugged it and tried starting it to drive it. Dash lights up, instruments function, but no starting noise it usually makes. When I put it in drive or reverse it will go nowhere with gas pedal depressed. Afterwards I can't turn off the car. Weird so I guess I'll get it towed to Chevy dealer on Monday. Any idea what's happening?
There is something else wrong. That is not the fail-safe behavior of this group of DTCs. (just the SHVCS message and loss of charging is)
You've got something else going on now. Please start a new thread! ;)
WOT
 

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Thanks I suspected the same and tried jump starting Volt after rolling car in Neutral out of garage. I thought maybe the starting Battery?
That didn't work. Power steering doesn't work either. I started a new thread. Volt power train battery has a nearly full charge.
 

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Thanks I suspected the same and tried jump starting Volt after rolling car in Neutral out of garage. I thought maybe the starting Battery?
That didn't work. Power steering doesn't work either. I started a new thread. Volt power train battery has a nearly full charge.
It's working again. Removed leads to 12v battery waited a few minutes and reconnected. It started right up. Drove it into garage and reconnected 240v charger. It is now accepting the charge. Thanks!
 

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Another P0AA6 fault

I finished packing my wife's 2012 for a weekend trip, jumped in and got the infamous " service high voltage charging system" message. Apparently she noticed it a couple days ago but didn't know what it meant. I called OnStar and the only code was P0AA6. Since it was already packed I just continued on the trip with no problems.

The dealer found no additional codes and only performed a "software upgrade". This sounds like they just reset the battery resistance to ground threshold that has been mentioned here. Covered under warranty.

Unrelated service. I had heard a low drone sound from the front end. Dealer determined that I had a bad wheel hub. They fixed it no problem. First paid service, other than two oil changes, in 67,000 miles.
 

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It's working again. Removed leads to 12v battery waited a few minutes and reconnected. It started right up. Drove it into garage and reconnected 240v charger. It is now accepting the charge. Thanks!
You're saying the SHVCS message and codes went away pulling the 12v? This would be great news.
 

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Yes the codes were cleared and it is functioning normally still. I talked to the dealership and an Onstar advisor this morning. They said removing 12v battery leads does clear codes (just like it did on many of my older cars) The bad news is the dealer and ONstar have no way of researching what my original problem was. I don't own a battery load tester so Im going to get the 12v battery checked to make sure it's OK. It is after all a 4 year old lead acid battery.
 

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You're saying the SHVCS message and codes went away pulling the 12v? This would be great news.
Well I drove my car this morning on a short drive came home parked it in the garage and plugged it in. It wouldn't accept a charge. I unplugged it and tried starting it to drive it. Dash lights up, instruments function, but no starting noise it usually makes. When I put it in drive or reverse it will go nowhere with gas pedal depressed. Afterwards I can't turn off the car. Weird so I guess I'll get it towed to Chevy dealer on Monday. Any idea what's happening?
Actually this owner experienced a different scenario (possibly a 12V issue)
This owner had a simple "no charge" condition (obviously with other non-coolant level related DTCs) There may have been an "Unable to Charge" message -but again, that is a totally different scenario. (usually 12V, J1772 receptacle, or even public EVSE error related)

Pulling 12V may clear certain DTCs but IT WILL NOT clear MOST of the critical codes on the Volt as they are stored in non-volatile memory.

As such, pulling 12V WILL NOT reset the "Service High Voltage Charging System" (SHVCS) message and associated DTCs as they are intentionally "latched" and unaffected by 12V reset. (if only it were that easy lol)

The ONLY way to clear the SHVCS message and P1FFx series of DTCs is to reprogram HPCM2.
WOT
 

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Actually this owner experienced a different scenario (possibly a 12V issue)
This owner had a simple "no charge" condition (obviously with other non-coolant level related DTCs) There may have been an "Unable to Charge" message -but again, that is a totally different scenario. (usually 12V, J1772 receptacle, or even public EVSE error related)


Pulling 12V may clear certain DTCs but IT WILL NOT clear MOST of the critical codes on the Volt as they are stored in non-volatile memory.

As such, pulling 12V WILL NOT reset the "Service High Voltage Charging System" (SHVCS) message and associated DTCs as they are intentionally "latched" and unaffected by 12V reset. (if only it were that easy lol)

The ONLY way to clear the SHVCS message and P1FFx series of DTCs is to reprogram HPCM2.
WOT
Not trying to contradict but the dealer told me the same thing when I went to get my 12v battery checked yesterday. He said error messages would still be able to be seen by him when they hooked up their equipment despite Onstar not reading any codes. After an hour he returned the car to me no charge because he said my car had no codes. His tech told him I had cleared them by removing 12v battery leads? He also said he could find nothing wrong with car despite the no propulsion problem on Sunday? Here's hoping it stays "fixed". Maybe non-critical codes were cleared?
 
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