What causes fault code P0380?

• Most likely: Defective glow plug(s) (open element internal to the plug) • Likely: Failed glow plug relay or Glow Plug Control Module (GPCM) • Possible: Blown high-amp glow plug fuse (typically 60-80A) • Possible: Corrosion or poor connection in the glow plug harness/bridge • Rare: Wiring harness break or short to ground between ECU and relay

Powertrain (Engine & Gearbox)Standard EOBD

P0380 - Glow Plug/Heater Circuit "A" Malfunction

Q: What are the symptoms of fault code P0380?

• Check engine light (MIL) illuminated • Glow plug indicator light flashes or fails to illuminate • Hard starting in cold conditions • Excessive white/grey smoke from exhaust after startup • Rough idle/misfires during warm-up phase • Increased DPF soot accumulation as regeneration may be inhibited

Q: How do you fix fault code P0380?

STEP 1: Check the main glow plug fuse (often 60A+ in the engine bay). Inspect the wiring harness for signs of melting or corrosion. STEP 2: Test glow plug resistance. Disconnect the leads and measure between the plug tip and engine ground. Target: 0.5 - 2.0 Ohms. Infinite resistance (OL) indicates a failed plug. STEP 3: Verify voltage supply at the plugs during 'Wait to Start' phase. Note: Modern systems may use PWM (Pulse Width Modulation) and lower voltages (5V/7V), check service manual. STEP 4: Use a diagnostic tool to command the Glow Plug Relay/Module 'ON' and monitor voltage drop and amperage draw. A healthy system should draw substantial current (e.g., 40-80A total depending on cylinder count). STEP 5: Replace faulty components. If replacing plugs, apply penetrating oil and perform the task on a warm engine to prevent breakage.

Last updated:1 February 2026

Related:Glow Plug, Glow Plug Relay, Glow Plug Control Module (GPCM), Main fuse, ECT

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0300

Random or Multiple Cylinder Misfire Detected

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

Technical Description

Diagnostic Trouble Code (DTC) P0380 points to a malfunction within the glow plug heater circuit 'A'. The Engine Control Unit (ECU) monitors the electrical integrity of the glow plug system by measuring current draw and voltage feedback. When the ECU signals for pre-heating or post-heating and senses an out-of-range value (such as an open circuit, short to ground, or high resistance), P0380 is triggered. The 'A' usually refers to the entire circuit or a specific bank of plugs depending on the manufacturer. This fault often triggers 'Limp Home' mode on modern Euro 5/6 engines to prevent excessive emissions or DPF clogging during warm-up.

Possible Causes

Defective glow plug(s) (open element internal to the plug)

Failed glow plug relay or Glow Plug Control Module (GPCM)

Blown high-amp glow plug fuse (typically 60-80A)

Corrosion or poor connection in the glow plug harness/bridge

Wiring harness break or short to ground between ECU and relay

Symptoms

Check engine light (MIL) illuminated

Glow plug indicator light flashes or fails to illuminate

Hard starting in cold conditions

Excessive white/grey smoke from exhaust after startup

Rough idle/misfires during warm-up phase VIDA.

Increased DPF soot accumulation as regeneration may be inhibited

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P0380 - Glow Plug/Heater Circuit "A" Malfunction

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P0380 - Glow Plug/Heater Circuit "A" Malfunction

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