P067A

Code

Generic P — Powertrain

Cylinder 4 Glow Plug Control Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 30 EN: 38 RU: 22

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Page language: EN

Causes

Open or high-resistance wiring to glow plug #4
Corroded/loose connector at glow plug or relay/module
Failed glow plug (open or short)
Faulty glow plug relay or power distribution fuse
Defective glow plug control output in ECM/PCM
Intermittent wiring short to ground or high resistance in harness

Symptoms

MIL (check engine light) illuminated
Hard or prolonged cold starting, especially in cool conditions
Excessive white smoke during cold start
Rough idle after cold start
Reduced fuel economy during warm-up

What to check

Read stored freeze frame and live data with a scan tool; note glow plug command and status
Check for related DTCs (other glow plug cylinder codes, power/ground circuit codes)
Visually inspect glow plug wiring, connector, and ground for corrosion or damage
Verify power supply fuse/relay for glow plug circuit and operation
Backprobe glow plug connector and measure voltage while commanding glow plugs on via scan tool
Measure resistance of glow plug #4 (engine cold) and compare to other cylinders

Signal parameters

Supply voltage to glow plug bank when commanded: typically ~11–14 V (vehicle battery voltage)
Glow plug element resistance (cold, typical range): ~0.5–5.0 ohms (manufacturer-specific)
When commanded, control output may be switched or PWM; duty cycle 0–100% depending on strategy
Open circuit indicated by very high/infinite ohms at glow plug winding
Low voltage (

Diagnostic algorithm

Connect a scan tool, confirm P067A and review freeze-frame/live data. Attempt a commanded glow plug ON/TEST if available and observe command/state.
Visually inspect connector and wiring at cylinder 4 for corrosion, bent pins, heat damage, or loose terminals. Repair or clean as needed.
With ignition off, disconnect glow plug connector and measure resistance of glow plug #4 to ground. Compare to other cylinders. Replace if open or far out of range.
With a backprobe or breakout harness and safe procedures, command glow plugs ON and measure voltage at the glow plug supply terminal. If battery voltage is present, suspect the glow plug itself or ground.
If commanded voltage is low or absent, check the glow plug supply fuse(s) and relay. Verify relay operation and measure voltage at relay output while commanded.
Check continuity and resistance of wiring between ECM/driver module and cylinder 4 connector. Repair any high-resistance joints or damaged wiring.
If wiring, fuses, relays, and glow plug appear OK but the control output does not change when commanded, suspect ECM/PCM driver fault and verify by comparing outputs for other cylinders or referencing manufacturer pin-out and bench-testing if available.
After repairs, clear codes and perform multiple cold start cycles or relevant readiness checks to ensure code does not return.

Likely causes

Corroded connector at cylinder 4 glow plug
Broken or pinched wire in harness to cylinder 4
Failed glow plug element (open) on cylinder 4
Faulty relay/fuse supplying glow plug bank
ECM control transistor or driver failed

Fault status

⚠️ Status

P067A — Cylinder 4 Glow Plug Control Circuit Low: low voltage or open/abnormal signal detected on the glow plug control circuit for cylinder 4. Glow plug may not heat; check wiring, connector, fuse/relay, glow plug element, and ECM driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.0 hours