P1391

Symptoms

• Difficulty starting the engine (especially in cold weather)
• Unstable engine operation after starting
• Increased exhaust smoke
• Check Engine Light on Dashboard
• Reduced engine power

Causes

• Faulty glow plug
• Open or short circuit in the glow plug circuit
• Problems with the relay or glow plug control module
• Contact corrosion
• Malfunction of the engine control unit (rare)

How to Fix

1. Check the resistance of the glow plugs
2. Inspect wiring and connectors for damage
3. Check the voltage at the glow plugs
4. If necessary, replace faulty glow plugs
5. Check and, if necessary, replace the glow plug relay

Related codes

Error P1391 by Vehicle Brand