P06BF

Code

Generic P — Powertrain

Cylinder 7 Glow Plug Circuit Range/Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 25 EN: 32 RU: 23

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Page language: EN

Causes

Open, short or high-resistance wiring/connectors in cylinder 7 glow plug circuit
Failed or internally shorted glow plug (cylinder 7)
Corroded or loose terminal/ground at glow plug or harness
Faulty glow plug relay, fuse or power supply
PCM/ECM driver fault or internal failure
Incorrect or low battery voltage during test

Symptoms

Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
Hard cold starts or extended cranking, especially in cold conditions
Rough idle or misfire at startup
Increased white/gray smoke or elevated emissions during warm-up
Possible engine diagnostic trouble codes for glow/heater circuits

What to check

Read and record freeze-frame and live data (glow plug command, status, and battery voltage) with a scan tool
Visual inspection of cylinder 7 glow plug connector, wiring, and ground for corrosion, damage or loose terminals
Check fuse(s) and relay(s) for the glow/heater circuit
Measure DC voltage at the glow plug connector during glow command (key ON/engine start conditions)
Measure glow plug resistance (ohms) with connector disconnected
Perform continuity and wiggle tests on wiring from the connector to the PCM/relay

Signal parameters

Supply voltage at glow plug during command: typically ~9–14 V (varies by vehicle), should be near battery voltage
Glow plug DC resistance (typical range): roughly 0.2–6 Ω (depends on plug type; consult OEM spec)
Expected current draw per glow plug: typically a few to tens of amperes (varies by plug type)—an unusually low or zero current indicates open circuit; very high current indicates shorted plug
Control signal may be steady or PWM/duty cycle; frequency and duty vary by manufacturer—scan tool should show command duty cycle or ON/OFF status

Diagnostic algorithm

Retrieve freeze-frame and live data with a capable scan tool; note battery voltage and glow plug command when code set.
Visually inspect cylinder 7 glow plug connector, wiring harness, and engine ground. Repair any obvious damage or corrosion.
With ignition OFF, disconnect cylinder 7 glow plug connector. Measure glow plug resistance to engine block (ground) with a multimeter. Compare to OEM spec. If resistance is open or out of spec, replace the glow plug.
With connector disconnected, measure continuity from the harness connector to the relevant PCM terminal (or relay output) to check for open/high resistance. Repair wiring as required.
With a helper or using a scan tool, command the glow circuit ON and measure DC voltage at the harness connector. If voltage is near battery voltage, power is present; if not, check fuse/relay/power feed.
Measure current draw (if safe and equipment available) during glow cycle to verify typical current. Low/zero current suggests open circuit; excessive current suggests shorted plug or harness.
Swap the suspected plug with a known-good plug on another cylinder (if practical). Clear codes and retest: if code moves to the other cylinder, the plug is faulty; if it remains on cylinder 7, the wiring/driver is suspect.
Inspect/replace glow relay and fuses if power feed is intermittent or missing.
If wiring, relay and glow plug check good, test PCM driver output (scope recommended) for correct command waveform. If driver is faulty, consult manufacturer procedures before replacing PCM.
After repair, clear codes and perform verification drive or repeated cold-start cycles to confirm repair and absence of code.

Likely causes

Corroded/loose connector at cylinder 7 glow plug
High-resistance or open wiring to cylinder 7
Failed glow plug on cylinder 7
Failed glow plug relay or blown fuse affecting feed to multiple plugs
PCM driver fault (less common)

Fault status

⚠️ Status

ECM detected cylinder 7 glow plug/heater circuit response outside expected range (voltage, current or resistance) indicating possible open, short, high resistance, or failed glow plug/driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours