P066CCylinder 2 Glow Plug Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Modern diesel glow systems switch each glow plug through its own power semiconductor (in a glow plug module or the engine module), so current and faults can be measured per plug; a faulty channel is switched off. CARB requires glow plugs to be checked for correct current and voltage drop and, since model year 2010, a single plug outside specification to be detected and named. P066C means the circuit to the cylinder 2 glow plug is shorted to ground or draws overcurrent. GM's engine-module drivers flag a circuit impedance to ground below 0.11 Ω (10 of 20 samples at 100 ms) with the check engine and glow plug lamps after two trips; Ford's 2023 Power Stroke checks during heating for more than 22 A for 0.3 s or 20–22 A for 2 s. The channel is switched off, so plug 2 no longer heats – harder cold starts and white smoke follow. A plug shorted internally is the usual cause; a wrong plug type is another.
- What you may notice
- Check engine and glow plug lamp
- Harder cold start, especially in frost
- Rough running and white smoke right after a cold start
- Possibly blown glow system fuse
- Likely causes
- LikelyGlow plug cylinder 2 shorted internally (element against body)
- PossiblePlug wire insulation damaged and shorted to ground (block, bracket)
- RareWrong plug type (resistance or voltage rating)
- RareDriver in the glow or engine module faulty, or software (GM 3.0 L 2020)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €60 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.