Chevy and GMC Duramax Diesel Forum - Reply to Topic
01-04.5 LB7 Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

Thread: OBD scanner not connecting/no reset Reply to Thread
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  Topic Review (Newest First)
11-22-2019 07:34 PM
whodgson Oh, jeez - didn't realize I'd posted in the wrong section. Sorry.

It is an '04 LB7.

If I understand the wiring correctly, the controller positive is always hot via the 175A fuse. I noticed while swapping out the controller that there was another wire that disappears under some tubing that is also attached to that post. Not sure where that goes.

I will undertake further checks per your suggestions. Thanks. At this point, though, I think it's going to be worth it to just take it to a pro. Gotta get it smogged by the end of the month.
11-21-2019 06:47 PM
Hook'em_Horns! Okay, my bad. I scanned back at what I saw a while back and it was "glow plug/Heater"...but their meaning was actually a GPH without the /.

Is this an LB7 '04 or an LLY '04.5?
Because you've posted in the LBZ section...with an '04

Check the fuse.
Check the wiring (said covered) and the post connections (easy to snap the wire crimp)
You checked the continuity of the wires....
Check at each GP's post end, not the wire. Make sure each shows a solid ground.

Just throwing things out..
11-21-2019 06:10 PM
whodgson See my reply below.
11-21-2019 05:21 PM
whodgson I just checked the intake heater. It showed 0.9 ohms and I saw 5.6v on the lead when I started the engine. Is that normal? I've not found anything about the inlet heater except how to do a delete plug, which won't work here in California as it's part of the emissions.
11-21-2019 04:31 PM
Hook'em_Horns! ....and the heater?
11-21-2019 02:25 PM
whodgson Okay so if I'm correct the positive wire on the controller is constantly 12v even with the engine off, which would also indicate that the 175A fuse would be good, yes?

Well, I changed out the controller and still get the P380 code. The gp circuits still show good. What am I missing?
11-21-2019 02:41 AM
whodgson I've just learned that the 175A fuse might be the culprit. Gonna pop the fuse box off and check that out before I do anything.
11-21-2019 02:00 AM
but the code came back after a couple of miles,
on a hot engine?
Also, I saw where the intake heater was part of that circuit too. Might take a look-see there.
But on a hot engine, both of those shouldn't be relevant, I would think.
11-21-2019 01:34 AM
whodgson Yes, it was one a dozen "tricks" that didn't work.
11-21-2019 01:32 AM
Originally Posted by Hook'em_Horns! View Post
It may be that you still have a problem, as to why the code re-appears.

P0380 Glow Plug Circ Error Circ A, relates to wiring/power to the circuit....

Bad GP/module would be P067x
What did you replace?
I neglected to mention that this is a California emissions vehicle.

At this point I've only replaced a glow plug and checked the wires from the module to the plugs to confirm continuity. All show about 1.6 ohms, rather than the open circuit that showed on the bad one.

I borrowed a better scanner from a coworker which was able to do the reset but the code came back after a couple of miles, at which point I checked everything again. It all still showed good, so the only thing left is the module.
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