Powertrain, generic · Computer and auxiliary outputs

P06C4 Cylinder 12 Glow Plug Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The glow module calculates each plug's resistance from voltage and current while glowing. 'Range/performance' means the circuit is electrically intact but the resistance or current lies outside the specified window – typically an aged, high-resistance or wrong plug or contact resistance at the connector. CARB requires a single plug outside specification to be detected from model year 2010. Ford's 2023 6.7 L/3.0 L Power Stroke runs this check during heating after the open and short checks and flags a circuit above 2 Ω after about 3 s. GM does not use this code family. No manufacturer document available to us uses this code for cylinders 9 and above; the description follows cylinders 1–8. P06C4 concerns the glow plug of cylinder 12 alone; the same plug's open circuit is P0682, its control circuit low and high P06E2/P06E3, and an incorrect plug fitted P06D0.

Likely causes

Glow plug cylinder 12 aged or high-resistance
Contact resistance at plug connector or terminal nut
Wrong plug type or a plug with a manufacturing fault
Engine or glow module software (Ram 6.7 L from 2025)

Symptoms

  • Check engine and glow plug lamp
  • Harder cold start in frost
  • Rough running and white smoke after a cold start
  • Often no symptom when warm

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

glow plugglow plug wiringglow plug control module

Related codes

P0682P06E2P06E3P06D0P0670P052F

References: law.cornell.edu, techtips.ie, fordservicecontent.com.