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DTC codes / P06xx · Computer and output circuits / P06C6

P06C6Cylinder 2 Glow Plug Incorrect

P06C6 means the engine control module has detected that cylinder 2's glow plug circuit is not performing as expected, typically because the measured electrical current or voltage does not match the profile for a healthy glow plug during the afterglow or preheat phase. The computer compares the commanded glow plug operation against feedback from the glow plug control module and flags an incorrect condition when the circuit resistance or current draw falls outside the expected window.

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

Symptoms you may notice

  • Illuminated check engine light or glow plug warning lamp, often with no other symptoms besides the warning light
  • Hard cold starting or extended cranking before the engine fires, especially in low ambient temperatures
  • Rough idle and white smoke from the exhaust immediately after a cold start
  • Reduced engine power or limp mode in some vehicles when the fault is active
  • Slightly increased fuel consumption during warm-up because the affected cylinder runs cold
  • Intermittent misfire codes or a pending misfire on cylinder 2 during cold operation

Common causes, most likely first

  1. Failed glow plug on cylinder 2, typically an open circuit or excessive resistance in the heating element
  2. Damaged or corroded electrical connector at the cylinder 2 glow plug, causing high resistance or intermittent contact
  3. Chafed, burnt, or open wiring in the glow plug harness between the control module and cylinder 2
  4. Faulty glow plug control module that cannot deliver or monitor current correctly for one channel
  5. Poor engine ground or corroded ground strap that skews the current feedback for the glow plug circuit
  6. Carbon buildup or oil contamination on the glow plug tip that alters its electrical characteristics
  7. Engine control module software or internal driver fault, though this is the least common cause

How to diagnose and fix it

  1. Scan all modules and record freeze-frame data for P06C6, then clear the code and verify whether it returns after a cold-soak key-on cycle
  2. Visually inspect the cylinder 2 glow plug connector, harness, and ground points for corrosion, chafing, or loose pins
  3. Measure the resistance of the cylinder 2 glow plug with a multimeter and compare it to the manufacturer's specification or to a known-good cylinder
  4. Check for voltage and current on the glow plug circuit during the preheat phase using a clamp meter or oscilloscope to confirm whether the control module is commanding the plug correctly
  5. Swap the cylinder 2 glow plug with another cylinder and see whether the fault follows the plug or stays with the cylinder, which isolates the plug from the wiring or module
  6. Test the glow plug control module outputs and grounds according to the service information if the plug and wiring test good
  7. Replace the faulty glow plug, connector, or control module as indicated by testing, clear the codes, and verify correct cold-start operation and no return of P06C6

Glow plug faults that fool good technicians

  • A glow plug can pass a simple resistance check at room temperature yet still fail to draw the correct current when hot, so a clamp meter during the preheat phase is more reliable than an ohmmeter alone.
  • The glow plug control module often stores P06C6 when the plug is fine but the connector has a poor crimp that only opens up when the engine bay is cold, so wiggle-test the harness while watching live glow plug current data.
  • Some vehicles set this code from a voltage supply issue to the glow plug control module rather than a fault in the plug itself, so check the module's power and ground feeds before condemning the plug.
  • Replacing only the faulty glow plug on a high-mileage engine often leads to repeat codes on neighbouring cylinders soon after, because the remaining plugs are equally worn and draw different current.
  • P06C6 can be stored as a history code after a single cold-start glitch and may not indicate a hard failure, so always verify the fault is current before authorizing parts replacement.

Can I keep driving with P06C6?

You can generally drive the vehicle with P06C6, but cold starting will be harder and the engine may run rough or smoke until it warms up, so avoid heavy load and long idling in cold weather. Have the fault diagnosed soon, because prolonged operation with a failed glow plug can lead to carbon fouling and eventual injector or cylinder wear.

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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