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DTC codes / P06xx · Computer and output circuits / P06CA

P06CACylinder 6 Glow Plug Incorrect

P06CA indicates that the engine control module (ECM) has detected an incorrect electrical condition in the glow plug circuit for cylinder 6, typically an open circuit, short to ground, or short to power. The ECM monitors glow plug current and voltage during the afterglow phase and sets this code when the feedback signal does not match the expected value for that cylinder.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaComputer and output circuits

Symptoms you may notice

  • Illumination of the check engine light or glow plug warning lamp, often with no other symptoms
  • Hard starting or extended cranking when the engine is cold
  • Rough idle or misfire immediately after a cold start that may improve as the engine warms
  • Excessive white smoke from the exhaust during cold starts
  • Reduced fuel economy and increased emissions during warm-up
  • In rare cases, a no-start condition in very cold weather

Common causes, most likely first

  1. Failed glow plug on cylinder 6 (open heating element or shorted internally)
  2. Damaged or corroded electrical connector at the cylinder 6 glow plug
  3. Chafed, broken, or shorted wiring in the glow plug harness near the cylinder 6 plug
  4. Faulty glow plug control module (GPCM) or relay that cannot supply or monitor current correctly
  5. Poor engine ground connection affecting the glow plug circuit
  6. ECM software calibration issue or internal driver fault (less common)

How to diagnose and fix it

  1. Perform a visual inspection of the cylinder 6 glow plug, connector, and wiring for damage, corrosion, or looseness
  2. Use a scan tool to command the glow plug on and measure voltage and current at the cylinder 6 glow plug with a multimeter or current clamp
  3. Check the resistance of the cylinder 6 glow plug with an ohmmeter and compare it to the specification for the engine
  4. Test the glow plug control module output and ground circuit integrity with a load test or oscilloscope
  5. If the glow plug is faulty, replace it and clear the code, then verify the repair with a road test and scan tool data
  6. If wiring or connector is damaged, repair or replace the affected section of the harness and retest
  7. If the control module is defective, replace it and reprogram or relearn as required, then confirm the code does not return

Glow Plug Code Traps You Should Not Fall Into

  • A P06CA for cylinder 6 does not always mean the glow plug itself has failed; a poor connection at the glow plug control module or a chafed harness can produce the same incorrect current reading.
  • Many technicians replace the glow plug without checking the afterglow phase, but this code often sets only during afterglow when the ECM expects a specific current draw that a weak plug cannot meet.
  • The glow plug control module may store this code even when the plug is good if the engine ground strap is corroded, so always verify ground integrity before condemning parts.
  • On some engines, a failed glow plug can cause a misfire code to set alongside P06CA, leading to unnecessary ignition system repairs if the glow plug fault is not addressed first.
  • Clearing the code without repairing the root cause will usually result in the code returning after one or two cold start cycles, so always complete the diagnostic steps before resetting.

Can I keep driving with P06CA?

You can generally continue driving with P06CA, but cold starting may be difficult and the engine may run rough until warm; avoid extended driving with a known misfire and address the fault before winter or whenever cold-start performance worsens.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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