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Discussion Starter · #1 · (Edited)
2014, 74k total, 60k EV and 15k gas.
I replaced the 12v battery about 6 months ago because it was old, not failing. Video of dash during startup.

Opening the hood will not start the engine.
First thing I did was check the 12 volt bus and got 12.5 to 12.8 during start. I checked all the fuses I know of (hood, rear, both doors) all appear good.

A couple oddities, dash thinks it's -40 degrees outside and onstar status shows all tires flat. When the hood is opened and the car is on, sometimes the electric fans come on full speed.

Car is unmodified except for led head and turn lamps and a dash cam. All were done many years ago.

The only issue I've had is a p015a code related to o2 sensor that seems intermittent. I don't drive on gas nearly enough to know for sure.

Any help would be greatly appreciated. Car is at work and I can tow it home or to the dealer, much prefer to tow it home. I have a vcx nano with gds2 so I can be dangerous so to speak.

It sounds like the classic failing 12 volt battery but its been replaced recently and seems fine. Almost seems like a ground is failing or a portion of the data network isn't working. Unfortunately I don't have the codes, I forgot to save them so I'll get them tomorrow. I tried asking Onstar to pull them but they could not do it remotely.
 

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Failing 12v battery is what I would have guessed as well. It's a $200 "diagnostic fee" to try a new battery. But yes, check the battery terminal straps are not lose.
 

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It sounds like some sort of a Can buss communications problem. You would need to connect the Nano up and see what you get or take to dealer (I can't help but think of Vegas when I use that word) and see how they deal with you.
 

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Discussion Starter · #4 ·
I'm hoping that's all it is. If I connect a replacement battery, do all the codes and faults clear themselves or do I have to clear them manually?

If that's not it, what do you suggest starting with?
 

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As far as I know you have to clear them with the Nano. Some codes are protection hard lock codes that require the module to be re-flashed.
 

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Try a cold boot. Disconnect battery. Leave 10 minutes, longer is better. Measure battery voltage across terminals. If over 12V, reconnect battery. Start the car. Does it work? Cost to diagnose if a cold boot will work. $0.00.
 

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i was going to suggest a poor connection to the module under the front left fender (I had damage to this fender that munged this cable, and got similar codes) - maybe by a squirrel or mouse chewing on wires, but you wrote it's at work, so that seems unlikely.
And if it happened while sitting, a loose connection seems unlikely, but trying to re-seat some of thing seems like a decent thing to try.

The earlier suggestion to connect the nano and see what is found on the CAN bus also makes a lot of sense.

-Lumos 2014 gen 1
 

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Discussion Starter · #8 ·
Battery terminals seemed tight. Disconnected the service battery neg and removed the HV disconnect for 10 min, plugged HV back in, reconnected neg and tried to start but got same as yesterday.

I plugged in the nano in and using the CAN bus tool, found the CAN bus + shorted to ground. Granted I don't know much about CAN bus troubleshooting so maybe you experts can help. Here is a screen grab of the CAN bus tool on my laptop.
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CAN bus shorted to low voltage, I'm assuming this means shorted to ground? Or is it possible that the CAN bus tool can show this if incorrectly configured or used? When it comes to CAN, I really don't know what I am doing but willing to learn. I've been troubleshooting engines with OBD2 for many years on my own cars and professionally, I work on large control and data acquisition systems.

GDS2 gave me this when polling vehicle wide DTC info.
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The first listing where it can't talk to the ECM is interesting, unless the engine must be running for it to communicate.

I tried clearing codes but that did not help.

I'm starting to worry that this is a broken wire shorting the CAN bus to ground. Lumos, your post intrigues me because I had body work done involving the left fender and door a few months back. Maybe during reassembly a harness got crushed? I'll have to check the service manual for the harness location.

I'm getting her towed home today so hopefully I can do more than poke at it in my company parking lot.
 

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I had an issue that was typical of a bad AGM. It ended up being a loose connection at the +12 connection from the power supply feeding the battery. The connection was interment and the battery voltage would get low causing issue. The plastic around the connection was melting and it was obvious by sight of the issue.
 

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Discussion Starter · #10 ·
I had an issue that was typical of a bad AGM. It ended up being a loose connection at the +12 connection from the power supply feeding the battery. The connection was interment and the battery voltage would get low causing issue. The plastic around the connection was melting and it was obvious by sight of the issue.
I'll check it out, thank you.
 
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