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Howdy!

I’m posting as a last ditch effort to help before I have the dealership drop the battery in my poor Volt. I have a 2012 with the Service High Voltage System message for about 1 month now. The car drives fine, battery doesn’t charge (it does regenerate a little just from normal regen braking — not sure if that makes a difference). I had the same message last year in December which was resolved by updating the BECM. I took it to the dealer and basically he said he needs to drop the battery in order to diagnose. He said this after all of his initial diagnostic tests didn’t show the root cause of the problem. The biggest thing according to the mechanic is that the “insulation resistance test” is showing 0.0 kohm.

I had him replace the coolant level sensor and that did nothing. The cost for just the labor to drop the battery is over $1k so I’m hoping someone else has an answer that doesn’t involve that.

I’ve attached some reports from the dealership. Thanks so much for all the input!

P.S. I had a Volt tech from another group tell me that if the insulation test was actually 0.0 kohm, the car wouldn’t even start. The mechanic ran the test twice and came back 0 both times.
Note that item 14 on the service report indicates the hybrid/ev battery isolation test Passed.
 

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I think it is a testing process
as more items in the test get run and pass more tests are then run

plus some of the recalls changed the firmware to allow (short answer - different values to pass- )

I would not expect a diagnostic machine to print a value as zero when is was really " test not run"

My dealer said they need a volt tech to run their machine when testing volts.
I have made thousands of resistance measurements over my career. When I knew that I was measuring a dead short, very rarely was 0.0 Ohms displayed. So to me, it is questionable.
 
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