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Discussion Starter #1
A couple of nights ago my wife had our '14 Volt out shopping. All was well during the prior trip. When she pushed the power button she got an odd driver's screen with the CEL lit and the battery icon replaced by a tiny battery icon with no color detail, just a plus at one end and a minus at the other.

She was able to take the shifter out of park and move it to other positions but the car wouldn't move.

OnStar told her "Hybrid Control Processor Power Train Sys detected malfunction related to engine control system. Electric Propulsion system not performing as expected." Towed it to dealer. They found two codes, P0AC4 and P06AF, basically saying the same thing.

They scanned and "reset" it, and said they loaded some updates. They're saying they hadn't seen this. My wife is concerned about it happening again.

Any thoughts?

-randl
 

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Change the 12 Volt battery would be the first thing to do, low voltage causes all types of reported issues as different modules work and others don't as the voltage level falls
 

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DTC P0AC4: Hybrid Powertrain Control Module Requested MIL Illumination
The hybrid powertrain control module has set an emission related DTC.

DTC P06AF: Torque Management System Performance - Forced Engine Shutdown
The hybrid powertrain control module does not detect a valid state of health message from the ECM.
The hybrid powertrain control module requests the hybrid control module 2 to open the high-voltage contactor relays.

When the high-voltage contactor relays are open, the Volt will not move under its own power.

Sounds like the hybrid powertrain control module didn't like what the engine control module had to say, so the propulsion power was shut down.

Glad they fixed your Volt and it is back on the road!
 

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I agree with Henry that the place to start would be the 12v. Failing 12v batteries have been responsible for any number of bizarre error messages. If you have serious sounding error messages that just go away, the 12v has to be the prime suspect. Plus it's easy to check.
 

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Discussion Starter #5
Is it possible to test the 12V battery? Seems odd to just change it when it still starts the car.
 

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Is it possible to test the 12V battery? Seems odd to just change it when it still starts the car.
What do you mean "starts the car"? The 12V battery has nothing to do with the ICE, and looking at your post, the other day when your wife was done shopping it failed to start the car :)

Take the car to autozone and ask them to test the 12V battery. Most cars they can test it with the battery still in the car and hooked up, but I personally wouldn't trust their test equipment to "play nice" with the Volts computer systems, so I would take the battery out and take it too them for testing.

Keith
 

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I had the 12 volt battery tested in my 2011 Volt by two different auto parts stores, and they both passed it.

Couldn't hurt to get it tested, I suppose.
 

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I'm not convinced that auto-parts-store battery testing is all that valid for Volts. Most car batteries only care that they're delivering 3000 watts to the starter motor for five seconds, and it doesn't matter if that happens at 12v or 10. Volts need a steady 12v available through the booting of about 30 little computers and switching a couple dozen relays, and the battery dropping to 10 volts during that is probably going to screw up the order of things enough to set an alert.
 
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