P0380 P0xxx · Powertrain (P) Medium severity
Glow Plug / Heater Circuit A Malfunction
A diesel cold-start aid circuit is open or drawing wrong current. Cold starts become hard and smoky, especially in winter.
Severity guidance: Medium — drivability or emissions affected, book it in this week
Symptoms you will notice
- Hard cold starting
- White smoke on start-up
- Rough idle when cold
- Glow plug warning lamp on
Common causes
Ordered from most to least likely — start at the top.
- 1 Failed glow plug
- 2 Blown glow plug fuse or failed relay
- 3 Open wiring in the harness
- 4 Faulty glow plug control module
How to diagnose it
Cheapest and least invasive first — most of these codes are not a parts problem.
- ✓ Measure current draw of the glow plug circuit — compare total draw with specification.
- ✓ Test each plug's resistance individually; open or shorted plugs stand out.
- ✓ Check the relay/fuse and the control signal from the ECU.
- ✓ Inspect the busbar and wiring for corrosion.
Repair options
- Replace failed glow plugs (usually as a set)
- Replace the relay or fuse
- Repair the harness
P0380 — frequently asked questions
Should I replace just the failed plug? +
Replace the set. Mixing old and new plugs gives uneven heating and the code often returns.
Why is it fine in summer? +
Compression heat alone is enough to start a warm engine; the glow system only matters when cold.
Confirm the diagnosis before you buy parts
Send us the code, freeze-frame data and the vehicle — our engineers will tell you what to test first.