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Home / DTC / P06C0 — Cylinder 8 Glow Plug Circuit Range/Performance

P06C0 — Cylinder 8 Glow Plug Circuit Range/Performance

Detailed page for trouble code P06C0.

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Code

P06C0

Generic P — Powertrain

Cylinder 8 Glow Plug Circuit Range/Performance

Brand: Generic
Type: P — Powertrain
Views: UK: 20 EN: 31 RU: 14
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Page language: EN

Causes

  • Failed glow plug in cylinder 8
  • High resistance or open in glow plug wiring or connector
  • Corroded or loose ground for glow plug circuit
  • Failed glow plug driver/relay or fuse
  • Short to voltage or short to ground in the harness
  • Poor connection at ECM/PCM or connector pins

Symptoms

  • Hard starting when engine is cold
  • Rough idle or misfire during warm-up
  • Increased white or blue smoke on cold start
  • Glow plug or check engine warning lamp illuminated
  • Longer than normal crank time before engine fires
  • Intermittent code or performance loss on cold starts

What to check

  • Read and record freeze frame data and related codes with a scan tool; check glow plug control commands and statuses.
  • Visually inspect glow plug wiring, terminals, and connectors at cylinder 8 for corrosion, damage, or loose connector.
  • Check fuses and glow plug relay operation related to the glow system.
  • Measure voltage at the glow plug terminal while the ECM commands preheat (expect near battery voltage or PWM output).
  • Measure resistance of the glow plug (with battery disconnected) and compare to specification / other cylinders.
  • Perform a current draw test on the glow plug circuit if safe equipment is available.

Signal parameters

  • Supply voltage during preheat: typically close to battery voltage (approx. 11–14 V) or specified PWM average.
  • Glow plug resistance (cold): typically low ohms — often under a few ohms (check manufacturer spec).
  • Circuit current draw: varies by plug type (single-digit amps per plug for many designs) — compare to spec or other cylinders.
  • Driver duty cycle / PWM percent when commanded: 0–100% depending on control strategy.
  • Response time: glow plug should reach expected current quickly when commanded (within a few hundred ms).

Diagnostic algorithm

  1. Connect a scan tool, confirm P06C0 and any related codes (P067x, P06Cx). Review freeze frame and live data for glow command, status, and battery voltage.
  2. Visually inspect cylinder 8 glow plug, connector, and wiring for damage, corrosion, or loose pins. Repair any obvious issues.
  3. Check fuses and glow relay. Activate glow preheat via scan tool and verify relay clicks and supply voltage present at the relay output.
  4. With battery disconnected, measure resistance of the cylinder 8 glow plug and compare to specification and to other cylinders. Replace plug if out of range or open.
  5. Command the glow circuit ON with a scan tool and measure voltage at the glow plug terminal (or use current clamp) to confirm proper voltage/current flow while commanded.
  6. Perform a voltage-drop test on positive and ground sides of the circuit (engine running or commanded) to find high resistance connections. Repair wiring or clean terminals as needed.
  7. If the plug and harness appear good, test the glow driver output at the ECM/PCM connector for proper switching (observe with meter or oscilloscope). If driver output is absent or abnormal while command is present, suspect relay/driver or PCM.
  8. If necessary, swap the cylinder 8 glow plug with a known good plug from another cylinder and retest to determine whether the plug or wiring/driver is at fault.
  9. After repairs, clear codes, perform several cold-start cycles and verify the code does not return and that cold-start performance is restored.
  10. If intermittent or no fault found in wiring/plug/relay, consult manufacturer service information for PCM tests, updates, or retesting procedures.

Likely causes

  • Defective glow plug in cylinder 8
  • Corroded/loose connector or high-resistance wiring to cylinder 8 glow plug
  • Faulty glow plug relay/driver or blown fuse protecting the circuit
  • Poor ground at engine block or harness ground strap
  • Less likely: PCM output driver failure or internal module fault

Fault status

⚠️ Status
Cylinder 8 glow plug circuit range/performance fault — circuit output out of expected range or not responding correctly.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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