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P codepowertrainMedium severity

P06C7Cylinder 3 Glow Plug Incorrect

The glow plug control module has determined that the glow plug installed in cylinder 3 does not match the expected type, based on its electrical signature.

Definition

During pre-heat the glow plug control module profiles each plug's resistance and current-versus-time behavior and validates it against the specified plug for the application. P06C7 sets when the cylinder 3 plug's signature indicates a wrong type or voltage rating — a frequent result of installing a standard metal plug where a low-voltage ceramic plug is specified, or vice versa. The module typically derates or disables that channel, causing hard cold starts and cold smoke with a glow plug lamp or MIL, and an incorrect plug left in service can overheat and suffer element or tip failure.

Common causes

  • Wrong voltage-rating or wrong-type glow plug fitted to cylinder 3
  • Aftermarket plug that does not match the OE electrical signature
  • Heavily degraded plug reading like an incorrect part
  • Terminal or harness resistance corrupting the module's measurement
  • Incorrectly coded or wrong-variant glow plug control module

Common misdiagnoses

  • Replacing the glow plug control module when the plug is the wrong part
  • Chasing wiring faults when the plug rating is incorrect
  • Replacing all glow plugs when only cylinder 3 is mismatched
  • Battery replacement for a signature-validation fault

Troubleshooting steps

  1. 1.Confirm the part number

    Verify the cylinder 3 plug against the OE catalog, checking voltage rating and element construction for this engine variant.

  2. 2.Measure resistance

    Measure the plug cold and compare to spec and the other cylinders; a distinctly different reading points to a wrong or failed plug.

  3. 3.Check the circuit

    Inspect the terminal, nut, and harness for corrosion or damage that adds resistance to the measurement path.

  4. 4.Profile the current

    Amp-clamp cylinder 3 during a commanded pre-heat and compare against a known-good cylinder's curve.

  5. 5.Install the correct plug

    Replace with the OE-specified plug at proper torque (typically 10-15 Nm), avoiding overtightening in an aluminum head.

  6. 6.Retest

    Clear codes and cycle pre-heat repeatedly to confirm the module now accepts the plug.

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