P0380
Glow Plug/Heater CircuitAP0380 is a generic OBD-II powertrain diagnostic trouble code: Glow Plug/Heater CircuitA. It is logged by the engine control unit when the glow monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0380 means
P0380 is set when the PCM (or on many diesel applications, a dedicated Glow Plug Control Module / GPCM) detects a malfunction in the glow plug or grid heater circuit on bank/group "A". Glow plugs are the cold-start heating elements fitted to diesel engines; they are energised before and during cranking to raise combustion chamber temperature so diesel fuel will ignite reliably at low ambient temperatures. On multi-bank configurations, "A" designates the primary bank or the first group of cylinders.
The control circuit works as follows: the PCM monitors coolant temperature and, when conditions call for pre-heat, commands the glow plug relay or GPCM to apply battery voltage to the glow plug(s). The module then checks for the expected current draw or voltage feedback from the circuit. P0380 is logged when the feedback indicates a fault — either too little current (open circuit, failed glow plug, blown fuse) or unexpected circuit behaviour (relay stuck open, wiring fault). The MIL illuminates and, depending on strategy, the wait-to-start indicator light on the dashboard may also activate.
The practical consequence is impaired cold starting. In mild temperatures, the engine may still start after extended cranking; in sub-zero conditions, it may not start at all. White exhaust smoke and excessive noise at cold start are typical symptoms. Addressing the fault promptly is important because repeated cold-start abuse without functioning glow plugs accelerates engine wear.
Common causes
Most-frequently reported root causes when P0380 is logged.
-
1
One or more failed glow plugs in bank "A" with an open-circuit element causing insufficient current draw.
-
2
Faulty or burnt-out glow plug relay that fails to close and apply voltage to the circuit.
-
3
Glow Plug Control Module (GPCM) internal failure preventing correct energisation of the bank "A" circuit.
-
4
Open circuit, short to ground, or high-resistance connection in the glow plug wiring harness.
-
5
Blown fuse in the glow plug supply circuit.
-
6
Corroded or loose glow plug connector reducing contact and increasing circuit resistance.
-
7
Low battery voltage causing the glow plug system to fall below the activation threshold.
-
8
PCM or GPCM software fault requiring a calibration update.
Symptoms drivers notice
How to diagnose P0380
A typical diagnostic flow when this code is present.
-
1
Connect a scan tool and confirm P0380 is stored; check for companion codes (P0381 indicator circuit, other cylinder bank glow codes).
-
2
Inspect the glow plug fuse and relay for the bank "A" circuit; replace any blown fuse or relay that does not actuate.
-
3
With the ignition in the pre-heat position, measure voltage at each bank "A" glow plug connector; 11–12 V should be present when the system commands on.
-
4
Measure each glow plug's resistance — a serviceable plug measures 0.5–2 Ω; open circuit or very high resistance indicates a failed plug.
-
5
Inspect wiring and connectors from the relay/GPCM to each plug for corrosion, chafing, or broken conductors.
-
6
Check battery voltage and condition; a weak battery may prevent the glow system from operating correctly.
-
7
If a GPCM is fitted, check for its own diagnostic codes using a manufacturer-specific scan tool, as generic OBD may not expose GPCM fault detail.
-
8
Confirm system operation after repair by monitoring glow plug current draw with a clamp meter during the pre-heat cycle.
Related powertrain codes
Frequently asked questions
Does P0380 mean all glow plugs have failed?
Not necessarily. P0380 covers the entire bank "A" circuit, so a single failed glow plug with an open element, a bad relay, or a wiring fault can set the code. Testing each component individually will determine whether the fault is in one plug, the relay, the GPCM, or the wiring.
Can I drive with P0380?
In warm weather, the engine will typically start and run normally because glow plugs are only needed below certain coolant temperatures. However, cold-weather starting will be severely impaired or impossible, and repeated hard cold starts without pre-heat accelerate cylinder and injector wear. The fault should be repaired before the next cold season.
What is the difference between P0380 and P0381?
P0380 is a fault in the glow plug heating circuit itself — the components that actually warm the combustion chamber. P0381 is a fault in the indicator lamp circuit — the dashboard warning light that tells the driver to wait for pre-heat. They can occur independently; P0381 does not necessarily mean the heaters have failed.
Is P0380 a petrol engine code?
No. Glow plugs are a diesel-engine technology. P0380 will only appear on diesel-powered vehicles. Petrol engines use spark plugs and do not have a glow plug pre-heat system. If this code appears on a petrol vehicle, suspect a data entry error or scan tool misidentification.
Disabling P0380 in software
RaceTune can permanently disable P0380 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P0380 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
Upload your file