Fault code P0381 – a step-by-step guide to diagnosing and fixing it

Error code P0381 is displayed and the check engine light is on - what does this mean?

The OBD/EOBD system has detected a fault in the glow plug heating circuit control. This DTC P0381 mainly occurs in diesel vehicles and indicates that the glow plugs are not working properly. For various manufacturers, this trouble code may also be referred to as "Glow Plug/Heater Circuit A".

What causes can this fault code have?

• Defective glow plugs
• Damaged glow plug relay
• Broken cables in the glow plug circuit
• Corroded plug connections
• Defective glow plug control unit
• Blown fuse in the glow plug circuit
• Poor ground connection
• Faulty wiring between ECM and glow plug system

What symptoms occur in parallel with fault code P0381?

• Starting problems: The vehicle is difficult or impossible to start in cold temperatures
• Extended starting time: The engine takes considerably longer to start, especially in winter
• White smoke: White or blue smoke comes out of the exhaust during a cold start
• Jerking when idling: The engine runs unevenly, especially in the first few minutes after starting
• Increased fuel consumption: The diesel engine consumes more fuel than usual
• Check engine light: The check engine light is permanently lit or flashing

How can I fix the problem with fault code P0381?

• Repairing Fault Code P0381 requires a systematic approach to identify the faulty component.
• Replace the glow plugs: Check all glow plugs and replace defective plugs with new OEM parts, as several often fail at the same time
• Replace glow plug relay: Locate the relay in the fuse box, check for continuity and replace with a new relay if defective
• Repair wiring: Check all cables from the control unit to the glow plugs for breaks or corrosion and replace damaged cables
• Check fuses: Check the glow plug fuse in the fuse box and replace with a new fuse with the correct amperage if blown
• Replace the control unit: If a defective glow plug control module is suspected, have it replaced with a programmed spare part
• Clean ground connections: Clean and tighten all ground points of the glow plug system and treat with contact spray