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2002 Chevrolet 2500HD 6.6L LB7 - P0380 Glow Plug Malfunction Circuit A Diagnosis & Solutions

Model: 2002 chevy 2500HD Fault Code: P0380 Posted: 2016-01-25 20:05

I own a 2002 Chevrolet 2500HD with the 6.6L LB7 engine (California emissions model) and am currently experiencing a P0380 diagnostic trouble code: 'Glow Plug Malfunction Circuit A'. I've already tested the power and ground connections at the glow plug control module — both are functioning properly. All glow plugs have been individually tested using an ohmmeter, showing resistance under 1 ohm, indicating they are in good condition. I also inspected all glow plug wiring for shorts or damage, and found no issues. The problem is that the vehicle's Powertrain Control Module (PCM) does not detect proper voltage changes when commanded to activate the glow plugs — which is what triggers the P0380 code. Since the module itself is not available locally in California and no Chevrolet dealerships carry it, I'm seeking reliable troubleshooting steps. Is there a way to test the glow plug control module without replacing it? What are common failure points in this system? Any guidance on identifying or sourcing a compatible replacement module would be greatly appreciated.

Related fault codes

P0380

Comments (9)

Anonymous 2016-01-26 09:31

You're in California — and yes, genuine glow plug modules for the CA-specific LB7 engine are hard to find. Do you have the part number for your module? Most likely, the issue lies with two specific wires connecting from the PCM to the module. Check this diagram: http://www.duramaxdiesels.com/forum/ima ... CM%208.gif

Anonymous 2016-01-26 18:16

Confirmed — no local dealerships carry the glow plug control module. All wiring from the PCM to the module has been tested and shows no shorts or continuity issues. The module receives full 12 volts when activated, so power delivery is not the problem.

Anonymous 2016-01-26 19:55

Try searching online for the exact module part number first. Before that, double-check your wiring: did you test for open circuits, short to ground, or short to voltage? Did you perform resistance checks on all wires? I'll look into the internal circuitry and logic of the module later — a P0380 code typically indicates the PCM isn't detecting expected voltage changes when commanded to activate glow plugs.

Anonymous 2016-01-26 20:38

I've verified all wiring from the PCM to the module — no shorts, no corrosion, and no breaks. I recently installed brand-new glow plugs, and surprisingly, the P0380 code hasn't returned. The truck has only 97,000 miles on it, which is well within normal service life.

Anonymous 2016-01-27 08:39

Keep searching for the module — availability will decrease over time. If you find one, consider whether the price is worth it. It might be a cost-effective option to source second-hand or from specialty suppliers.

Anonymous 2016-01-27 10:09

The local dealer just called and said they're receiving a small batch of modules in about a month — I may purchase two at $194 each as a backup.

Anonymous 2016-01-27 10:32

A helpful tip: ask the dealer how much it costs to install the module. Dealerships often offer lifetime repairs, meaning they’ll own the part after installation. Do the math — if labor is about 0.5 hours and the part costs $194, that’s roughly $200 total. Think of this as a form of insurance. Also, search for the exact part number to find current availability online.

Anonymous 2019-03-09 22:49

I found a glow plug controller at a GM Parts Outlet for $137.49 — part number 97226648. It's the flat-style module, not the square one with two relays. The dealer had no idea what I was talking about. This helped me resolve my issue. Also, don't forget to check fuse #175 (175 Mega-Amp) — it’s a common oversight that can cause similar symptoms.

Anonymous 2019-03-10 22:19

I finally resolved the P0380 code on my Duramax. I replaced the glow plug module, but the issue persisted. Then I suspected the 175 Mega-Amp fuse — which was blown. After replacing it, the knocking stopped and engine performance improved significantly. The transmission shifted smoother too. After turning off and restarting multiple times, the service light turned off completely. Now the truck runs much better. This simple fix made a huge difference — I hope this helps others. A blown 175 mega-amp fuse can severely impact engine function and should never be overlooked.