Help with P0380 code after disconnecting battery.

[JayDicky]

Thank you in advance.
Ok, here’s a weird one:

I have an 04 gmc 2500hd LB7. I had to remove driver side battery to reconnect the window wash fluid hose. The secondary was left hooked up. When I replaced the battery I went in the truck and my rear camera was on without key in ignition. When I went to turn on the truck the gauges didn’t move but dash lights came on. The truck started but the dash gauges were NOT moving. I then disconnected Bothell negative cables, on both batteries, turned on headlights and 15 minutes later rebooked the batteries and then cycles ignition 3 times and started on third. Started fine and all seemed back to normal. I did not drive it at this point. The next morning i started the engine and the engine light was on and a code P0380.
The truck seems to be starting and running fine.

The rear view cam was installed over a year ago with no problem, along with an Alpine ILX-650 stereo. It has the harness to maintain the steering wheel controls. I also drove the truck hoping the code would clear, but no luck.

Does anyone have any idea what it could be? I have since cleared the codes and am hoping engine light does not come back on.
I will report back tomorrow on that.
P0380: Glow Plug/Heater Circuit A

 

[DAVe3283]

P0380 usually means a failed glow plug. You can unplug the two connectors on the glow plug controller, and measure the resistance of each pin. It is an easy way to find which glow plugs(s) have failed. IIRC they should be a couple ohms, so if you find one that is much higher or lower than that, it is probably bad. Just swap out the glow plug(s) that failed, and you should be good to go.

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[JayDicky]

[

P0380 usually means a failed glow plug. You can unplug the two connectors on the glow plug controller, and measure the resistance of each pin. It is an easy way to find which glow plugs(s) have failed. IIRC they should be a couple ohms, so if you find one that is much higher or lower than that, it is probably bad. Just swap out the glow plug(s) that failed, and you should be good to go.

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Thank you. I used a scanner to clear the engine light yesterday and it hasn’t come back on. Do you think that disconnecting one battery could cause the weird electrical symptoms it had, and trip the engine light? Or is it more likely that a glow plug or relay is starting to go out? Just seems so weird and was wondering if anyone has a theory or has seen anything like this before. I like to believe it was an electrical glitch and all is well now, but I’m not sure that is a good ending either. Something strange happened. How long would it take for the engine light to come back on after clearing the code? It originally came on at startup, the morning after.
I’m baffled!

 

[DAVe3283]

The code should come back after 2 cold starts, I believe.

These trucks are super sensitive to electrical system problems, so it is possible that it was all a result of low voltage or something.

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[JayDicky]

The code should come back after 2 cold starts, I believe.

These trucks are super sensitive to electrical system problems, so it is possible that it was all a result of low voltage or something.

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Thank you brother Dave

 

[JayDicky]

Thank you brother Dave

Well, the check engine light came back on after 2nd cold start. Disconnecting the battery has to have something to do with it, can’t be a coincidence. Annoying! Thank you again

 

[zakkb787]

Glow plugs aren’t too expensive at the parts store. Make sure to get AC Delco OEM ones. That, a relay, and making sure the fuse is still good would be your first three things to check. You’ll have to take the under hood fuse block lower cover off to check the fuse. The one in my LB7 was blown at one point. Cheap easy fix. Same as the relay. Unplug and plug back in new one. If those don’t work, soak your plugs in PB Blaster a few times and then very carefully pull and replace. If I were a guessing man I’d say possibly the shock of completely taking the power from and then putting back could have used the fuse or relay to pop. Stranger things have happened. Also, just wondering, how old are your batteries?

 

[Ron Nielson]

See this: https://www.dtcdecode.com/Chevrolet/P0380

 

[JayDicky]

Glow plugs aren’t too expensive at the parts store. Make sure to get AC Delco OEM ones. That, a relay, and making sure the fuse is still good would be your first three things to check. You’ll have to take the under hood fuse block lower cover off to check the fuse. The one in my LB7 was blown at one point. Cheap easy fix. Same as the relay. Unplug and plug back in new one. If those don’t work, soak your plugs in PB Blaster a few times and then very carefully pull and replace. If I were a guessing man I’d say possibly the shock of completely taking the power from and then putting back could have used the fuse or relay to pop. Stranger things have happened. Also, just wondering, how old are your batteries?

After I drive the check engine light went off and stayed off for a few days but this morning when I started up the check engine light was back on again. What could cause that?
I thought I was out of the woods but apparently not.

 

[DAVe3283]

After I drive the check engine light went off and stayed off for a few days but this morning when I started up the check engine light was back on again. What could cause that?
I thought I was out of the woods but apparently not.

Did you check and/or replace any glow plugs? From what you've posted here, I get the impression you didn't actually do anything to the truck. The check engine light is trying to tell you what is wrong, but you have to put in a little work.

If you have CA emissions (EGR and a cat), the glow plug controller is a computer at the back left (driver's side) of the motor. Unplug to 2 outer connectors. Using a digital multi-meter, measure the resistance between each pin and ground. They should all read the same (around 1Ω I think), but if a glow plug has failed, it will typically be much higher. That will tell you which glow plug(s) need replaced.

Once you know which glow plug(s) are bad, replace them. That should fix the check engine light. If you need help tracing which pin goes where, I can probably dig up the wiring diagram.