Failed glow plug on cylinder 7 (open heating element or shorted internally); Damaged or corroded electrical connector at the cylinder 7 glow plug; Broken or chafed wiring in the glow plug harness near cylinder 7; Faulty glow plug control module or relay affecting that circuit; Poor ground connection for the glow plug circuit; Engine control module software issue or internal driver fault (less common)

DTC codes / P06xx · Computer and output circuits / P06CB

P06CBCylinder 7 Glow Plug Incorrect

Q: What does code P06CB mean?

Cylinder 7 Glow Plug Incorrect. P06CB indicates that the engine control module has detected an incorrect electrical condition in the glow plug circuit for cylinder 7, typically an open circuit, short to ground, or short to power. The module compares expected glow plug current or voltage against actual readings and sets this code when the values fall outside the acceptable range for that specific cylinder.

P06CB indicates that the engine control module has detected an incorrect electrical condition in the glow plug circuit for cylinder 7, typically an open circuit, short to ground, or short to power. The module compares expected glow plug current or voltage against actual readings and sets this code when the values fall outside the acceptable range for that specific cylinder.

SystemPowertrain

Code typeGeneric (all makes)

SeverityLow

Fix difficultyIntermediate

AreaComputer and output circuits

Symptoms you may notice

Illumination of the check engine light or glow plug warning lamp
Often no symptoms besides the warning light, especially in warm weather
Hard starting or rough idle when the engine is cold
Excessive white smoke from the exhaust after a cold start
Misfire or rough running during the warm-up period
Reduced fuel economy or increased emissions during cold operation

Common causes, most likely first

Failed glow plug on cylinder 7 (open heating element or shorted internally)
Damaged or corroded electrical connector at the cylinder 7 glow plug
Broken or chafed wiring in the glow plug harness near cylinder 7
Faulty glow plug control module or relay affecting that circuit
Poor ground connection for the glow plug circuit
Engine control module software issue or internal driver fault (less common)

How to diagnose and fix it

Perform a visual inspection of the cylinder 7 glow plug, connector, and wiring for damage or corrosion
Measure the resistance of the cylinder 7 glow plug with a multimeter and compare to specification
Check for voltage and ground signals at the glow plug connector during the glow plug activation period
Test the glow plug control module output for cylinder 7 using a bidirectional scan tool or oscilloscope
Repair or replace any damaged wiring, connectors, or ground connections found during testing
Replace the faulty glow plug if resistance is out of range or the element is open
Clear the diagnostic trouble codes and verify the repair by monitoring glow plug operation with a scan tool

Glow plug code traps you should not fall for

A glow plug that tests good on resistance can still be faulty under load, so always verify circuit operation with the glow plug energized if possible.
The code often sets intermittently due to a poor connection that only acts up in cold or damp conditions, so wiggle-test the harness while monitoring live data.
Replacing all glow plugs as a set is not always necessary, but on high-mileage engines a single failed plug often predicts others will follow soon.
The glow plug control module may store this code even when the glow plug itself is fine, so do not condemn the plug until the circuit has been properly loaded and tested.
Some vehicles use a glow plug with an integrated pressure sensor, and a fault in that sensor circuit can mimic a glow plug electrical fault, so check the exact plug type before ordering parts.

Can I keep driving with P06CB?

The vehicle is generally safe to drive with this code because the glow plug only affects cold-start performance and emissions, but avoid prolonged driving if you notice rough running or excessive smoke. Have the fault repaired before cold weather arrives to prevent hard starting and potential damage to the starter or battery from extended cranking.

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.