GM Volt Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
300 Posts
Discussion Starter · #1 ·
2017 with 88k miles. Zero issues before this. Battery was nearly full and I was in EV mode. Temperature outside about 58F.

I was at a stop light- accelerated from a stop with railroad tracks about 75 feet away. As soon as I hit the RR tracks my dash went crazy and the dreaded "Shift to Park" message displayed. A glance in my rear view had me looking at getting rear ended by a big truck approaching quickly and I could not get to the right due to heavy traffic- luckily I was able to make a hard left turn onto a side street with momentum and get out of danger zone.

The car was acting strangely - it would not shut off. Any time the shifter was moved it said "Shift to Park" and a check engine light was on. I finally got out of the car and used the remote buttons a few times- then got back in and it would shut off, but then it repeated all this on startup. So I got it to shut off again and went for a walk to get the remote away from the car; now it started and would let me drive!

Made it about 3 blocks and it dies again - same scenario.

Starts again and I gingerly drive it about 3 miles home.

Torque App and OBD reader says P0C04 - Powertrain, P0AC4 - Powertrain. Nothing else.
I checked the 12V battery connections and voltage. 13.23V with the car off. Same voltage at each of the connectors that come off the side of the battery.

Dealer can't get me in to see a Volt Tech until May 11th. I'm in a work situation where I'm on call 24/7 for the next few weeks.

Do I dare keep driving it?? Are there some easy things to check that I'm missing?
 

·
Registered
Joined
·
189 Posts
2017 with 88k miles. Zero issues before this. Battery was nearly full and I was in EV mode. Temperature outside about 58F.

I was at a stop light- accelerated from a stop with railroad tracks about 75 feet away. As soon as I hit the RR tracks my dash went crazy and the dreaded "Shift to Park" message displayed. A glance in my rear view had me looking at getting rear ended by a big truck approaching quickly and I could not get to the right due to heavy traffic- luckily I was able to make a hard left turn onto a side street with momentum and get out of danger zone.

The car was acting strangely - it would not shut off. Any time the shifter was moved it said "Shift to Park" and a check engine light was on. I finally got out of the car and used the remote buttons a few times- then got back in and it would shut off, but then it repeated all this on startup. So I got it to shut off again and went for a walk to get the remote away from the car; now it started and would let me drive!

Made it about 3 blocks and it dies again - same scenario.

Starts again and I gingerly drive it about 3 miles home.

Torque App and OBD reader says P0C04 - Powertrain, P0AC4 - Powertrain. Nothing else.
I checked the 12V battery connections and voltage. 13.23V with the car off. Same voltage at each of the connectors that come off the side of the battery.

Dealer can't get me in to see a Volt Tech until May 11th. I'm in a work situation where I'm on call 24/7 for the next few weeks.

Do I dare keep driving it?? Are there some easy things to check that I'm missing?
Do you have OnStar? If so, call them and ask for a remote diagnosis. They will email you all the codes and also list how severe the issue is and how long they recommend you drive with the issue too. It's actually quite an incredible service I have never seen anywhere. It will definitely tell you whether you can drive with confidence or be cautious. Torque Pro is not really that useful for digging into the sub codes like OnStar does.

Sent from my Pixel 4 XL using Tapatalk
 

·
Registered
Joined
·
3,373 Posts
P0C04 - Drive Motor "B" Current High - the control module for MGB is reporting too much current.

P0AC4 - Hybrid Powertrain Control Module requested MIL (Check Engine) Illumination - this is a secondary code and will clear when the primary P0C04 is corrected.
 

·
Registered
Joined
·
300 Posts
Discussion Starter · #6 ·
Do you have OnStar? If so, call them and ask for a remote diagnosis. They will email you all the codes and also list how severe the issue is and how long they recommend you drive with the issue too. It's actually quite an incredible service I have never seen anywhere. It will definitely tell you whether you can drive with confidence or be cautious. Torque Pro is not really that useful for digging into the sub codes like OnStar does.

Sent from my Pixel 4 XL using Tapatalk
So I decided to try this and wanted to "push the button" during the issue. Went for a drive and made a few stops running errands very local. Like 15 miles and 3 stops. It never recurred and the check engine light cleared on its own. Car feels normal. If/when it happens again I will see what On-Star diagnostics says. (I have the cheapest plan, so I hope it is part of the package).
 

·
Registered
Joined
·
300 Posts
Discussion Starter · #7 ·
P0C04 - Drive Motor "B" Current High - the control module for MGB is reporting too much current.

P0AC4 - Hybrid Powertrain Control Module requested MIL (Check Engine) Illumination - this is a secondary code and will clear when the primary P0C04 is corrected.
I heard a louder than normal Kuh-Clunk as I crossed the tracks.

Is it possible that the tires spun on the slippery metal rails and then caught traction on the asphalt and caused a current spike in MGB??

As I wrote above - the CEL has cleared after a short trip of errands.
 
  • Like
Reactions: jbakerjonathan

·
Registered
Joined
·
405 Posts
So I decided to try this and wanted to "push the button" during the issue. Went for a drive and made a few stops running errands very local. Like 15 miles and 3 stops. It never recurred and the check engine light cleared on its own. Car feels normal. If/when it happens again I will see what On-Star diagnostics says. (I have the cheapest plan, so I hope it is part of the package).
If it's under warranty take it in and have it diagnosed. Typically nothing good results when the CEL is illuminated and then is extinguished without a diagnosis as to why it was illuminated.
 

·
Registered
Joined
·
300 Posts
Discussion Starter · #9 ·
If it's under warranty take it in and have it diagnosed. Typically nothing good results when the CEL is illuminated and then is extinguished without a diagnosis as to why it was illuminated.
I'll be keeping my appointment in 10 days for sure.

Hate that I can't trust it like I used to and for a while I'll be riding cautiously in the right lane looking for a place to bail safely.
 
  • Like
Reactions: WhatAShocker

·
Registered
Joined
·
150 Posts
Is it possible that the tires spun on the slippery metal rails and then caught traction on the asphalt and caused a current spike in MGB??
This sounds plausible, especially if acceleration rate was high. I've had this occur but shows up as a low traction message with brake booster activation. Perhaps conditions were severe enough in your case that the main contactor opened briefly and caused the shutdown. You get a star for learning to drive more defensively.
 

·
Registered
Joined
·
189 Posts
I'll be keeping my appointment in 10 days for sure.

Hate that I can't trust it like I used to and for a while I'll be riding cautiously in the right lane looking for a place to bail safely.
If it was me, because I am that kind of guy, I would record a video and attempt to replicate the conditions of driving over the tracks as closely as possible. If you can trigger it to happen again, such evidence would be crucial to a) have a more rapid diagnosis by the dealer, b) put your mind at ease regarding how safe your car is to drive (may have been a chance event, 3) avoid the dealer telling you, your car was fine and they were unable to replicate the condition.

Give it some thought, though I do acknowledge your need to be available 24/7 however. I am siding with the high speed overspin condition, or car thinking it was momentarily air born, it could theoretically cause it and the car panicked and perhaps over reacted. Again, all theories. Hahaha.

Sent from my Pixel 4 XL using Tapatalk
 

·
Registered
Joined
·
3,373 Posts
Knowing how rough most railroad crossings are my suspicion is you have a loose power line somewhere that is causing this. It could even be an internal short in the sensor.
 
  • Like
Reactions: axle69 and Roostre

·
Registered
2017 Volt Premier Citron Green
Joined
·
55 Posts
The worst part of your problem is that it is intermittent. Hardest problems to diagnose. I agree with Shocker to try to replicate the problem while recording it. Also, even though your AGM battery reads good, might be a good time to replace it.
 
1 - 13 of 13 Posts
Top