P06C4

Code

Generic P — Powertrain

Cylinder 12 Glow Plug Circuit Range/Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 31 RU: 25

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Scan with a capable OEM-style scan tool for freeze frame and related codes
Visually inspect wiring, connectors, and pins for damage or corrosion at cylinder 12 and the control module
Check glow plug fuse(s) and relay operation
Measure battery voltage (engine off) to confirm adequate supply (typically ~12–14 V)
Command the glow plug ON with a scanner and observe current draw or status for cylinder 12
Measure individual glow plug resistance after isolating from harness

Supply voltage at glow plug connector when commanded ON: approximately battery voltage (nominally 11–15 V)
Typical glow plug resistance (varies by design): often low ohms; many types fall in roughly 0.1–3 Ω (compare to manufacturer spec)
Expected current draw per glow plug varies by design — commonly in the single-digit to low double-digit amps (e.g., ~4–20 A); compare measured current to OEM spec
Controller reports: ON/OFF status, commanded current or measured circuit current/voltage (if supported by the vehicle)

Read and record all DTCs and freeze frame data. Note related glow plug or module codes.
Visually inspect battery cables, ground straps, fuses, glow plug relay, and wiring to cylinder 12 for damage or corrosion.
With ignition off, disconnect the glow plug connector at cylinder 12 and measure resistance of the glow plug to engine ground. Compare to specification; a very high or infinite ohms indicates an open glow plug.
Reconnect and back-probe the connector. With a scan tool, command the glow plug ON and observe voltage at the connector and current draw (use clamp ammeter on feed if safe). Verify voltage approximates battery and current is within expected range.
If voltage is OK but current is low, suspect high resistance in plug, connector, or ground. If no voltage, suspect wiring/fuse/relay/module fault between power supply and plug.
Wiggle harness and connectors during activation to check for intermittent faults. Check for signs of overheating or melted insulation.
Swap plug with an adjacent cylinder (if the same type and wiring allows) and see if the fault follows the plug or stays with the cylinder position — this helps isolate plug vs. wiring/module.
If wiring and plug check good, test/replace the glow plug driver/module or related control unit following OEM procedures. Repair any corroded connectors or damaged wiring before replacing module.
After repairs, clear codes and perform multiple cold start cycles and a road/operational test to confirm the issue is resolved.