OBD-II Trouble Code Technical Description

Glow Plug/Heater Circuit “A”

What does that mean?

This code is a generic powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may be slightly different depending on the model.

The description for GM vehicles is just slightly different: Glow Plug Performance Conditions.

The glow plug operates when starting a cold diesel engine (the powertrain control module PCM uses the coolant temperature when the ignition is switched on to determine this). The glow plug heats up red hot for a short period of time to increase the cylinder temperature allowing the diesel fuel to ignite more easily. If there is an open in the glow plug or circuit this DTC will set.

On some diesel engines, the PCM will operate the glow plugs for a period of time after the engine is running to reduce white smoke and engine noises.

A typical diesel engine glow plug:

Basically, the P0380 code means that the PCM has detected a fault in the glow plug/heater circuit "A".

Note: This DTC is very similar to P0382 which that code refers to circuit "B". If you have multiple DTC codes, fix them in the order they appear.

Performing a quick Internet search shows that the P0380 DTC seems to be more common on Volkswagen, GMC, Chevrolet, and Ford diesel equipped vehicles, however is possible on any diesel vehicle (Saab, Citroen, etc.)

Symptoms

Symptoms of a P0380 trouble code may include:

Malfunction Indicator Lamp (MIL) illumination

Glow plug / Wait To Start indicator stays illuminated longer than normal (may be on solid)

Hard to start condition especially in colder weather

Potential Causes

Potential causes for this DTC may include:

Fault in glow plug wiring (open, short to ground, etc.)

Glow plug faulty

Open fuse

Faulty glow plug relay

Faulty glow plug module

Diagnostic Steps & Possible Solutions

If you have a GM truck or really any vehicle for that matter, check for known issues such as TSBs (technical service bulletins) that pertain to this code.

Check associated fuses, replace if blown. Test glow plug relay if possible.

Visually inspect the glow plugs, wiring, and connectors for corrosion, wiring pins bent/loose, loose screws/nuts on wiring connections, burnt appearance. Repair as necessary.

Check harness connectors for resistance using a digital volt ohm meter (DVOM). Compare to manufacturer specifications.

Disconnect glow plug wires, measure resistance using DVOM, compare to spec.

Use a DVOM to verify that the glow plug wiring connector is getting power and ground.

If replacing a glow plug, be sure to start it in the threads by hand first, just like you would a spark plug.

If you really want to test the glow plug, you could always remove them, apply 12V to the terminal and ground the body for a 2-3 seconds. If it glows red hot it’s good, if it’s a dull red or not red, it’s no good.

If you have access to an advanced scan tool, there may be functions you could use on it that pertain to the glow plug wiring circuit.

Other Glow Plug related DTCs: P0381, P0382, P0383, P0384, P0670, P0671, P0672, P0673, P0674, P0675, P0676, P0677, P0678, P0679, P0680, P0681, P0682, P0683, P0684.