P0380 The computer found a fault in glow plug circuit A on a diesel engine

Glow plug/heater circuit A malfunction

Severity not verified — if the car runs badly, have it inspected

The sources define the code and list causes but do not say how serious it is, so severity is not verified.

Source: how we rate severity

P0380 in short

P0380 means the engine computer found a fault in glow plug circuit A on a diesel engine. TroubleCodes.net lists bad glow plugs, damaged wiring, blown fuses, a faulty glow plug relay or control module and a coolant temperature sensor as causes. The usual sign is hard starting when the engine is cold.

Glow plugs heat the combustion chambers of a diesel so it starts when cold. P0380 is set when the computer sees a fault in the circuit labelled A. The Delaware DMV list and TroubleCodes.net give the same meaning.

Circuit A labelling varies by maker, so the service manual is needed to know which glow plugs or relay it covers. The glow plug controller also uses the coolant temperature reading, which is why TroubleCodes.net lists that sensor.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Defective glow plugs

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists defective glow plugs first.
    What would change this
    Rises if individual plug resistance is out of specification. Falls if all plugs test good.

  2. Faulty glow plug relay, blown fuse or fusible link

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists the relay, fuses and fusible links as causes.
    What would change this
    Rises if the fuse is blown or the relay does not switch. Falls if both work.

  3. Damaged, corroded or disconnected wiring or connector

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists wiring and connector damage.
    What would change this
    Rises if damage or corrosion is found. Falls if the circuit tests clean.

  4. Faulty engine coolant temperature sensor

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists it because the glow system relies on the coolant reading.
    What would change this
    Rises if the sensor reading is wrong against actual temperature. Falls if it reads correctly.

  5. Failed glow plug control module, ignition switch or (rarely) the computer

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net lists the control module and ignition switch, and calls the computer a rare cause.
    What would change this
    Rises if the plugs, relay, fuses and wiring all test good.
    How to test the engine control module (ecm / pcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all stored codes with a scan tool and check the coolant temperature sensor reading against the actual engine temperature.

    Low riskTool: OBD-II scan tool

  2. Check the glow plug fuses and fusible links and look over the wiring and connectors.

    Low risk

  3. Have a shop test the glow plug relay and each glow plug against the manual.

    Best left to a shopTool: multimeter

    Warning:Glow plug circuits draw high current, and the plugs and the engine area around them stay hot after use. Disconnect the battery and let the engine cool first, and avoid shorting the heavy feed wire.

Symptoms

  • Hard starting when the engine is cold
  • Engine will not start in cold weather
  • Glow plug warning light on

How to fix

  1. Check the glow plug fuses and fusible links in the fuse box against the owner's manual.

Parts and cost context

  • Engine control module (ECM / PCM):The computer is a rare cause; check plugs, relay, fuses and wiring first.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Volkswagen

  • 1999–2003 · Beetle

    Supported by vehicle data

    Volkswagen bulletin TT280109 says TDI glow plugs come from two suppliers (Bosch and Beru) and must not be mixed, or P0380 (glow plug monitoring) may set. Whether it is still current is not verified.

  • 1999–2003 · Golf

    Supported by vehicle data

    Volkswagen bulletin TT280109 says TDI glow plugs come from two suppliers (Bosch and Beru) and must not be mixed, or P0380 (glow plug monitoring) may set. Whether it is still current is not verified.

  • 1999–2003 · Jetta

    Supported by vehicle data

    Volkswagen bulletin TT280109 says TDI glow plugs come from two suppliers (Bosch and Beru) and must not be mixed, or P0380 (glow plug monitoring) may set. Whether it is still current is not verified.

  • TT280109Status unverified

    TDI glow plugs come from two suppliers; do not mix

    1999–2003beetle, golf, jetta · issued · NHTSA 10238596

    Volkswagen bulletin noting two suppliers (Bosch and Beru) for TDI glow plugs. The summary says all plugs on a vehicle must be from the same supplier or DTC P0380 (glow plug monitoring) may set.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2001–2004 · Silverado 1500

    Supported by vehicle data

    GM bulletin 01927 covers a no-charge condition with DTCs P0380 and P0621 on 2001-2004 models. Whether it is still current is not verified.

  • 01927 (chevrolet)Status unverified

    No-charge condition with DTCs P0380 and P0621

    2001–2004silverado-1500 · NHTSA 10007832

    GM bulletin for a no-charge condition with diagnostic trouble codes P0380 and P0621. The summary does not give the repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

GMC

  • 2001–2004 · Sierra 1500

    Supported by vehicle data

    GM bulletin 01927 covers a no-charge condition with DTCs P0380 and P0621 on 2001-2004 models. Whether it is still current is not verified.

  • 01927 (gmc)Status unverified

    No-charge condition with DTCs P0380 and P0621

    2001–2004sierra-1500 · NHTSA 10007832

    GM bulletin for a no-charge condition with diagnostic trouble codes P0380 and P0621. The summary does not give the repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for P0380 yet.

All Diesel emissions and glow plugs codes

P0380 questions

Can I drive with P0380?

The sources do not rate it. Once a diesel is running it may drive normally, but it may be hard to start in the cold, so get the glow plug circuit checked before winter.

Sources and review

  1. TroubleCodes.net P0380: glow plugs circuit A malfunction — TroubleCodes.net
  2. TT280109: TDI glow plugs come from two suppliers; do not mix — Volkswagen
  3. 01927: No-charge condition with DTCs P0380 and P0621 — General Motors
  4. 01927: No-charge condition with DTCs P0380 and P0621 — General Motors
  5. On-Board Diagnostic Trouble Codes (generic code title list) — Delaware Division of Motor Vehicles
Last reviewed
Written by
Saurabh K.
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