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P codepowertrainMedium severity

P06D0Cylinder 12 Glow Plug Incorrect

The glow plug control module has determined that the glow plug installed in cylinder 12 does not match the expected type, based on its electrical signature.

Definition

The glow plug control module profiles each plug's cold resistance and current ramp during pre-heat and validates the result against the specified plug for the application. P06D0 sets when the cylinder 12 plug's signature corresponds to a different plug type or voltage rating than expected, typically after an incorrect replacement part was fitted. The module may limit or disable drive to protect the element, resulting in hard cold starts, cold-start smoke, and a glow plug lamp or MIL; a wrong plug driven at full duty risks overheating and mechanical failure of the element tip.

Common causes

  • Wrong voltage-rating or wrong-type glow plug installed in cylinder 12
  • Aftermarket plug that does not match the OE electrical signature
  • Severely degraded plug presenting as an incorrect part
  • Terminal corrosion or harness resistance distorting the measurement
  • Wrong-variant or miscoded glow plug control module

Common misdiagnoses

  • Replacing the glow plug control module when the plug is the wrong part
  • Repeated wiring repairs when the plug rating is incorrect
  • Replacing the entire plug set when only cylinder 12 is mismatched
  • Charging-system diagnosis for a signature-validation fault

Troubleshooting steps

  1. 1.Verify the part number

    Compare the cylinder 12 plug against the OE catalog, confirming the correct voltage rating and element type for this engine.

  2. 2.Measure cold resistance

    Measure plug-to-ground resistance and compare with specification and with the other cylinders.

  3. 3.Check the circuit

    Inspect the terminal and harness for corrosion, looseness, or damage that adds resistance.

  4. 4.Profile the current

    Amp-clamp cylinder 12 during a commanded pre-heat and compare the curve with a known-good cylinder.

  5. 5.Fit the correct plug

    Install the OE-specified plug at proper torque (typically 10-15 Nm) after cleaning the plug bore.

  6. 6.Clear and verify

    Clear the code and run multiple pre-heat cycles to confirm the module accepts the plug signature.

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