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P codepowertrainMedium severity

P06C6Cylinder 2 Glow Plug Incorrect

The glow plug control module has determined that the glow plug installed in cylinder 2 does not match the expected type, based on its electrical signature.

Definition

The glow plug control module compares each plug's cold resistance and heating-current profile against the signature of the plug specified for the engine. P06C6 sets when the cylinder 2 plug behaves like a different plug type or voltage rating than the calibration expects — commonly after an incorrect replacement part is installed. The module may limit or disable drive to protect the element, resulting in hard cold starting, cold-start smoke, and a glow plug lamp or MIL; leaving a wrong high-draw plug in service risks element overheating and tip failure into the cylinder.

Common causes

  • Incorrect voltage-rating or wrong-type plug installed in cylinder 2
  • Non-OE aftermarket plug whose characteristics differ from specification
  • Badly degraded plug mimicking an incorrect part's signature
  • Circuit resistance from a corroded terminal skewing the measurement
  • Wrong-variant or miscoded replacement glow plug control module

Common misdiagnoses

  • Replacing the glow plug control module instead of the mismatched plug
  • Wiring repairs when the installed plug rating is wrong
  • Replacing the entire plug set when only cylinder 2 is incorrect
  • Charging-system parts for a plug-signature fault

Troubleshooting steps

  1. 1.Verify the plug part number

    Check the cylinder 2 plug against the OE catalog for this exact engine, confirming the correct voltage rating and element type.

  2. 2.Measure cold resistance

    Compare plug-to-ground resistance with specification and with sibling cylinders to spot an obvious mismatch.

  3. 3.Inspect the circuit

    Rule out corroded or loose terminals that could distort the module's current profiling.

  4. 4.Compare pre-heat current

    Amp-clamp the cylinder 2 feed and compare the inrush and settle curve with a known-good cylinder.

  5. 5.Fit the correct OE plug

    Install the specified plug at proper torque (typically 10-15 Nm), taking care with reach and thread condition.

  6. 6.Clear codes and verify

    Run several pre-heat cycles and confirm the incorrect-plug detection does not return.

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