Faulty glow plug on cylinder 9; Damaged or corroded electrical connector at the cylinder 9 glow plug; Open or shorted wiring in the glow plug circuit for cylinder 9; Failed glow plug control module or relay affecting that circuit; Poor ground connection for the glow plug circuit; Engine control module software issue or internal fault (less common)

DTC codes / P06xx · Computer and output circuits / P06CD

P06CDCylinder 9 Glow Plug Incorrect

Q: What does code P06CD mean?

Cylinder 9 Glow Plug Incorrect. P06CD is a generic powertrain code indicating that the engine control module has detected an incorrect condition in the glow plug circuit for cylinder 9, typically on diesel engines with individually controlled glow plugs. The module monitors the glow plug's electrical characteristics and sets this code when the feedback signal does not match the expected value for that cylinder.

P06CD is a generic powertrain code indicating that the engine control module has detected an incorrect condition in the glow plug circuit for cylinder 9, typically on diesel engines with individually controlled glow plugs. The module monitors the glow plug's electrical characteristics and sets this code when the feedback signal does not match the expected value for that cylinder.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Extended cranking time or rough idle when the engine is cold
White smoke from the exhaust after a cold start
Misfire or rough running during the warm-up phase
Reduced fuel economy or increased emissions during cold operation

Common causes, most likely first

Faulty glow plug on cylinder 9
Damaged or corroded electrical connector at the cylinder 9 glow plug
Open or shorted wiring in the glow plug circuit for cylinder 9
Failed glow plug control module or relay affecting that circuit
Poor ground connection for the glow plug circuit
Engine control module software issue or internal fault (less common)

How to diagnose and fix it

Inspect the glow plug connector and wiring for cylinder 9 for damage, corrosion, or looseness
Measure the resistance of the cylinder 9 glow plug and compare it to the manufacturer's specification
Check for battery voltage and ground at the glow plug connector during the glow plug activation period
Test the glow plug control module output for cylinder 9 with a suitable scan tool or oscilloscope
Replace the faulty glow plug if resistance is out of specification or the plug does not heat
Repair or replace damaged wiring or connectors in the cylinder 9 glow plug circuit
Clear the diagnostic trouble codes and verify the repair by performing a cold start and monitoring glow plug operation

Glow Plug Circuit Checks Before Replacement

A glow plug that tests good on resistance can still set this code if the control module's feedback circuit is faulty, so always verify the module's output signal.
Corroded terminals at the glow plug connector are a frequent cause of incorrect feedback and are often overlooked when the plug itself tests fine.
This code can be set by a weak battery or poor ground, as low voltage during glow plug activation can mimic a faulty plug.
On some engines, the glow plug control module is integrated into the engine control module, making diagnosis more complex and expensive if the module is faulty.
Do not replace all glow plugs just because one is faulty; address the specific cylinder and verify the circuit to avoid unnecessary repairs.

Can I keep driving with P06CD?

You can generally continue driving with this code, but cold starts may be rough and emissions can increase. Avoid heavy loads or long idling until the fault is repaired, and address it promptly to prevent further issues.

Tools that help

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