Engine

P0383 — Glow Plug Control Module Control Circuit Low

Severity: medium Safe to drive

What P0383 means

A diesel engine computer commands a glow plug control module or relay to heat the glow plugs before a cold start. P0383 sets when voltage or current in that module's control circuit is lower than expected. The usual culprits are the module itself, its power or ground supply, or the wiring.

Symptoms

  • Glow plug or check engine light on
  • Hard starting in cold weather
  • Long cranking before the engine fires
  • Rough idle until warmed up
  • White smoke at cold start
  • Higher emissions while cold

Possible causes

  1. Failed glow plug control module
  2. Damaged wiring or poor connector contact in the circuit
  3. Bad glow plug relay or blown fuse
  4. Worn or failed glow plugs
  5. Control wire shorted to ground
  6. Power, ground or communication problem with the engine computer

How to diagnose

  1. Scan for codes and review freeze frame data for other faults
  2. Inspect the glow plug fuses and relay
  3. Check the module connectors and harness for corrosion and damage
  4. Measure supply voltage and ground quality at the module
  5. Test the control signal from the engine computer to the module
  6. Measure resistance of each glow plug
  7. Check the harness for a short to ground
  8. If power and signal are good, suspect the module itself

Common fixes

  • Replace the glow plug fuse or relay
  • Repair damaged wiring and clean connectors
  • Replace faulty glow plugs
  • Replace the glow plug control module
  • Fix a poor ground or power supply problem

Questions and answers

What does P0383 mean?

The diesel engine computer found low voltage or current in the glow plug control module circuit. Cold-start preheating may not work properly as a result.

Can I drive with code P0383?

Usually yes, especially in warm weather. In the cold the engine will start hard, so get it repaired soon.

Where do I start diagnosing P0383?

Check the glow plug fuses and relay first, then the connectors and module ground. Replace the module or plugs only after those checks pass.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.