OBD Guide
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P066A

Cylinder 1 Glow Plug Control Circuit Low

P066A is an OBD-II diagnostic trouble code meaning: Cylinder 1 Glow Plug Control Circuit Low. Common causes: short circuit of the glow plug control wire of cylinder 1 to ground, damaged or broken wiring between gpcm and ecu. Estimated repair cost: $17–278.

Severity
⚠️ Medium
Can you drive?
Yes, but get it checked soon
Approx. repair cost
$17–278 (est.)

Symptoms

  • Difficulty starting a diesel engine in cold weather
  • The Check Engine light comes on
  • Increased starter cranking time when starting
  • Increased white smoke from the exhaust pipe during startup
  • Possible unstable engine operation after a cold start

Causes

  • Short circuit of the glow plug control wire of cylinder 1 to ground
  • Damaged or broken wiring between GPCM and ECU
  • Glow Plug Control Module (GPCM) Malfunction
  • Faulty glow plug of cylinder 1 (internal short circuit)
  • Oxidation or damage to control circuit connectors

How to Fix

  1. Read error codes with an OBD-II scanner, write down all active and saved codes
  2. Visually inspect the wiring and connectors of the cylinder 1 glow plug and GPCM
  3. Measure the voltage in the glow plug control circuit of cylinder 1
  4. Check the resistance of the glow plug of cylinder 1 (normal: 0.5–2 Ohm)
  5. Check control circuit for short to ground
  6. If the wiring is in good condition - diagnostics and replacement of the GPCM module or ECU

Related codes

P066BP0671P0670P066CP066D

Error P066A by Vehicle Brand

AcuraAudiBAICBMWBYDBuickCadillacChanganCheryChevroletChryslerCitroenDodgeDongfengExeedFAWFordForthingFotonGACGMGMCGeelyGreat WallHavalHondaHongqiHyundaiInfinitiJACJaecooJaguarJeepJetourKaiyiKiaLadaLexusLi AutoLifanLincolnLivanMazdaMercedes-BenzMercuryMitsubishiNIONissanOldsmobileOmodaOpelPeugeotPlymouthPontiacRenaultSWMSaturnSkodaSkywellSubaruSuzukiTankToyotaVolkswagenVolvoVoyahXPengZeekrZotye

FAQ

What does the P066A code mean?

P066A is an OBD-II diagnostic trouble code that indicates: Cylinder 1 Glow Plug Control Circuit Low

What causes a P066A error code?

The most common causes of P066A include: Short circuit of the glow plug control wire of cylinder 1 to ground; Damaged or broken wiring between GPCM and ECU; Glow Plug Control Module (GPCM) Malfunction; Faulty glow plug of cylinder 1 (internal short circuit).

How do I fix a P066A diagnostic trouble code?

To fix P066A: Read error codes with an OBD-II scanner, write down all active and saved codes. Visually inspect the wiring and connectors of the cylinder 1 glow plug and GPCM. Measure the voltage in the glow plug control circuit of cylinder 1. For a complete diagnosis, use an OBD-II scanner.

Is it safe to drive with P066A?

Yes, but get it checked soon

How much does it cost to fix P066A?

The estimated repair cost for P066A is $17–278. Actual cost depends on your vehicle, location, and labor rates.

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