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P0380 – Glow Plug Circuit – Mercedes OM651/OM642 diesel (Mercedes-Benz OM651 2.1 CDI)

Fault code P0380 means "Glow Plug Circuit – Mercedes OM651/OM642 diesel". It is common on OM651 2.1 CDI (C 200/220/250 CDI, E 220/250 CDI, Sprinter, Vito), OM642 3.0 V6 CDI (E 350 CDI, ML 350, Sprinter), OM646 engines. Below are the real-world causes, step-by-step tests and OEM part numbers.

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P0380 quick summary

Fault codeP0380
MeaningGlow Plug Circuit – Mercedes OM651/OM642 diesel
SystemPowertrain (Engine & Transmission)
VehiclesMercedes-Benz
Common onOM651 2.1 CDI (C 200/220/250 CDI, E 220/250 CDI, Sprinter, Vito), OM642 3.0 V6 CDI (E 350 CDI, ML 350, Sprinter), OM646
SeverityLow
Can I drive?Yes. Cold starts get difficult and the engine smokes, but in mild weather it drives normally.
Repair cost€60 – €700

Symptoms of P0380

  • Hard starting in cold weather
  • Glow plug warning light stays on or flashes
  • White smoke and rough idle after a cold start
  • Check engine light
  • Fault stored for a specific cylinder

Most common causes of P0380 (most likely first)

Mechanic's Pro Tip

Mercedes glow plugs, especially on OM651 and OM642, are known to seize in the cylinder head. Remove them warm, with penetrating oil and correct torque, and stop at the first sign of resistance – a snapped plug means drilling it out. Check the glow output stage (glow plug control unit) if several cylinders fail at the same time.

  1. 1.Burned-out glow plug

    Most likely

  2. 2.Faulty glow output stage (glow plug control unit)

  3. 3.Damaged glow plug connector or wiring

  4. 4.Supply or ground fault at the control unit

  5. 5.Wrong glow plug type fitted

Step-by-step diagnostic guide

  1. 1

    Read the engine control unit and note the affected cylinder.

  2. 2

    Measure each glow plug's resistance or check current draw.

  3. 3

    Inspect the connectors and wiring harness.

  4. 4

    Check supply and ground at the glow output stage.

  5. 5

    Replace the faulty plugs or the control unit, clear codes and test a cold start.

Frequently asked questions

What does a snapped glow plug cost?

Drilling out a broken glow plug can cost several hundred euros per cylinder, sometimes needing head removal. That is why careful removal is important.

Can I drive with a faulty glow plug?

Yes, but starting in winter gets harder and there is more soot, which loads the DPF faster.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.