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Discussion Starter #1
I drove my 2013 Gen1 volt to work yesterday and got the Service High Voltage Charging System message when started the car to go back home where I am unable to charge the car again. My battery coolant level has not changed from the level recommended (well above the seam of the tank). I installed the WOT defeat plug on my Volt a couple of years ago to prevent the faulty low coolant sensor from causing the message to appear requiring an ECU reflash at the dealer which will not be covered under warranty or free, only to have the problem reappear when the faulty sensor fails again. I disconnected the 12V battery and checked the defeat plug which is just a resistor to fool the ECU the tank is full. It read 25K ohms across it which is probably correct. From all the post I can find on the subject it looks like the coolant sensor failure (or low coolant level) is the only failure I can find that will set the fault codes and this message. I just ordered a VCXNano GDS2 adapter to see the fault codes, clear and see if they immediately come back. Then trouble shoot from there. I am a former automotive mechanic and now an electronics technician so I feel comfortable doing this, but I really didn't want to have to become a master volt technician to own this car. I figure instead of giving my chevy dealer my money, I would spend the $140 bucks on the Nano and GM software and at least be armed with information if I need to take it in. Has any one seen the message after installing the WOT defeat plug?
 

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I think that's a generic fault that numerous issues can cause. The GDS 2 with the nano should reveal the cause..

Sent from my LM-V405 using Tapatalk
 

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What exactly are the codes you're getting? A while ago I got the SHVCS message, I used Torque and found P1e00, P1ffb and P1fff. I was able to clear them (with Torque) and have had no issues since. Like you, the coolant levels are right on mark but my Volt has not the defeat plug for coolant level.
 

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Discussion Starter #4
Thanks for the suggestions. I do have a vgate OBD2 Scanner iCar2 Bluetooth Diagnostic Tool I bought to look at my battery cell levels before I take my Volt in for the Cell Balancing recall SB (all cell pack voltage levels were all well within tolerance at full charge, fully depleted, and half depleted) I use the MyGreenVolt app but I don't think it can read/clear fault codes. I'll install the Torque app if I can scan and clear codes with it.
 

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Thanks for the suggestions. I do have a vgate OBD2 Scanner iCar2 Bluetooth Diagnostic Tool I bought to look at my battery cell levels before I take my Volt in for the Cell Balancing recall SB (all cell pack voltage levels were all well within tolerance at full charge, fully depleted, and half depleted) I use the MyGreenVolt app but I don't think it can read/clear fault codes. I'll install the Torque app if I can scan and clear codes with it.
Any updates?
 

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Discussion Starter #6
I have been a little busy this week so I've been driving the car in HOLD mode. I was able to get the Torque Pro app on a spare Android phone (wasn't available for my iPhone). I had these fault codes stored: P1E00, P0AA6, P1FFF. I cleared the codes and I'm able to charge the car for about 30 minutes now with no problems. Doing a search for these codes, I see several cars have had this problem even with the WOT defeat plug installed. I'm trying to find a common problem and fix for this issue on the forum but seems to range from wiring harness/resistance issues to a simple software update will fix it. I'll see if I can get it fully charged and drive it to work tomorrow and see if the faults return. One thing I didn't go into on my first post, the night before the problem I was charging the car and a thunderstorm popped up and our lights at home started flickering. I ran down to the garage and unplugged the charger. I had a charger get fried from a lightning strike close to the house about 6 months ago. I've installed a lightning arrestor in the breaker box since. The next morning I finished charging the car and went to work (20 mile drive) where the message appeared when I got in it to leave. I hope the brief interruption in power may have set a code that didn't appear until later? I will update after driving tomorrow.
 

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I hope the brief interruption in power may have set a code that didn't appear until later? I will update after driving tomorrow.
Voltage flucuations can affect the charging and potentially set a code that will normally clear after several full charges/discharges.
 

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Discussion Starter #8
I believe the one or more of the fault codes are "latched" and will clear using the Torque Pro app and my OBD2 Scanner, but now the SHVCS message returns as soon as I pull out of the garage to head to work. I get the same P1E00, P0AA6, P1FFF codes every time I scan with the app. I'm glad I'm at least able to clear them long enough to charge for the next day but I want to fix it right. I have since found several post on here with the same problem I have and I've been reading through all of them to figure out my next step. My VCXNano GDS2 adapter hasn't arrived yet. When it gets here I'm going to try to jump through all the hoops to get it installed on my laptop. Sounds like a lot of Windows and Java versions issues and configuration issues to get it working but a lot of good info on here. With the GM software I should be able to update the ECU and battery control modules to the latest firmware which seems to be a permanent fix. I believe this is what the dealer will do if I take it in but I will have to fight to get it fix under warranty I'm sure. My Voltec warranty is almost expired so I might as well get ready to be able to diagnose and repair when software gremlins rear they're ugly heads.
 

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When I had those CODES I too had to use hold/MM to charge BUT only a dealer re-programming cleared the flags.

BUT the re-programming as part of the FREE battery cell recall re-programmed the correct modules.

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The WOT device will not protect from a wire to the computer bad connection problem.

Voltage isolation glitch and or 10 year old cooling fluid.

I got my codes while charging a SUPER hot car in sunlight on a 115 DEG day
charging quit - got the text message - tried to start car and saw those exact codes.

Drove on gas for 6 month - ( state inspection was a problem as well - as engine light was on )
 

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My son‘s 2014 volt with about 120,000 miles just got the usual 3 codes with the “service HV charging system message”. ( The WOT fix was installed last year) Was not able to charge. I sucessfully cleared the codes with a generic OBD tool. His car then charged sucessfully but as soon as he pulled out of the garage, the problem reoccurred. We will be investigating further. In a previous thread, WOT stated that low coolant is the ONLY condition that will set these codes. Assuming he’s correct, I’m going to check the WOT plug and the wiring between the plug and control module which, if I remember correctly, is under passenger seat. We have not had the battery balancing update done so we’ll try that first. We will be following this thread and will post if we correct the problem. Incidentally, we’re a 3 volt family - 2 2014s and a 2015. We love ‘em!
 

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Discussion Starter #11
Seems to be a very common issue with the "Service High Voltage Charging System" and the codes I'm seeing. I haven't done the battery balance update but I was planning to get it done once I confirmed my battery cells are in good shape. I'm a little hesitant to take the car in with fault codes. I'm sure they will find something expensive to replace. (sorry I used to work at a dealership some are great some not so much) I saw a post with the service procedures the technician will follow when seeing the message. Basically, check the coolant sensor and associated wiring, check for moisture or leaking at the HV battery drain, check isolation resistance for the HV battery, and reprogram the ECU module with latest updated software. I did check the WOT defeat resistor again and it does read right at 25K ohms which is what the ECU is looking for, I'm leaning away from a wiring harness problem for now. Anything is possible but I think the odds are slim. I haven't lost a drop of coolant or seen any drops in the garage so I'm not suspecting a coolant leak. I haven't seen anyone have a battery isolation resistance problem. That would be rare and I think related to a coolant leak in the battery compartment. I just received my VCXNano GDS2 adapter, but my cd drive in my laptop is damaged so I'm waiting on a new drive. I'll keep updating here soon as I can start the software updating.
 

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You mentioned that the coolant level was well above the seam. You should know that the level should be even with the TOP of the black label on the side of the tank, not the seam in the middle of the tank. You will find this information in the list for WOT Sensor.
 

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Thanks for the suggestions. I do have a vgate OBD2 Scanner iCar2 Bluetooth Diagnostic Tool I bought to look at my battery cell levels before I take my Volt in for the Cell Balancing recall SB (all cell pack voltage levels were all well within tolerance at full charge, fully depleted, and half depleted) I use the MyGreenVolt app but I don't think it can read/clear fault codes. I'll install the Torque app if I can scan and clear codes with it.
The "car scanner" app is a great free app that I have used for many months now and has a bunch of volt features as well as code clearing.
 

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Discussion Starter #14
After checking my Voltec warranty expiration (Dec this year), I decided to take my Volt to my local dealership to fix the SHVCS message issue. I disconnected the 12V battery and removed the WOT defeat plug and put back to original configuration with the battery coolant level sensor connected. I fully charged the HV battery and made sure the SHVCS message was set with the check engine light lit and removed my OBDII bluetooth adapter before I dropped it off. The service department plugged in a his handheld scanner to see the codes that were set and it also ran my VIN for software updates. They performed the Service Bulletin for the SHVCS message and did the cell balancing software update that I needed no charge. I've had my Volt back for about a week with no issues. My range of ~42 mile per charge seems to be about the same as before so I assume the battery cells were fairly balanced with no weak cells. I will disconnect the 12V battery and reinstall the WOT defeat plug in the next few days because the tank level sensors are proven to be faulty.
 
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