P067C — Cylinder 5 Glow Plug Control Circuit Low

What are the symptoms of P067C?

Drivers most often notice: Check Engine Light on, glow plug warning light staying on, rough idle until warmed up, hard starting in cold weather.

How much does it cost to fix P067C?

Replace one glow plug — $80–$200; Replace the glow plug relay/module — $150–$450; Replace a full set of glow plugs — $250–$600. Exact cost depends on the root cause, your vehicle and local labor rates — a proper diagnosis is the cheapest first step.

Is it safe to drive with P067C?

Safe to drive once the engine is started and warmed up. The main risk is cold-weather starting: with several dead plugs the engine may not start on a cold morning. Fix before winter.

Will P067C clear itself?

Sometimes P067C clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

How do I diagnose P067C myself?

Start with a scan: confirm P067C, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the cylinder 5 glow plug control, and verify the suspect component against live data before buying parts.

When your vehicle's computer detects a problem with the heating elements that help diesel engines fire up in cold temperatures, it logs code P067C. This specific trouble code points to "Cylinder 5 Glow Plug Control Circuit Low" — meaning the electrical signal governing that particular cylinder stays stuck near ground voltage instead of pulsing as it should. The powertrain control module (PCM) logs P067C only after confirming the fault persists across multiple test cycles, preventing false triggers from temporary glitches.

Diesel glow plugs work like miniature heaters threaded directly into each cylinder's combustion chamber. When you turn the key in cold weather, the PCM energizes these plugs for several seconds, raising cylinder temperatures so the fuel ignites cleanly. The system relies on precise voltage switching — a control circuit that swings between 12 volts and ground. When something pulls that signal permanently low, P067C appears. Cylinder numbering follows the front-to-back belt-end convention on inline engines, though V-configurations vary by manufacturer. This matters because cylinder 5 sits deeper in the engine bay on some layouts, potentially requiring intake manifold removal for access.

The PCM monitors glow plug performance through feedback signals. If cylinder 5's control circuit reads as grounded when it should be hot, the module assumes either a failed switch, wiring damage, or a missing power supply. Freezing the conditions at the moment of failure helps you reproduce the exact scenario — usually a cold start — when testing. Without this snapshot, diagnosis becomes guesswork.

Common symptoms of P067C

• Check Engine Light illuminates on the dashboard
• Glow plug warning indicator remains lit after engine warm-up
• Engine runs rough or lopes noticeably until operating temperature is reached
• Difficulty starting the engine, especially in freezing conditions
• White smoke billowing from the exhaust pipe following a cold start
• Reduced overall engine performance in colder ambient temperatures

What causes P067C?

• Burned-out or internally failed cylinder 5 glow plug drawing the circuit low
• Broken or corroded connector at the cylinder 5 glow plug terminal
• Wiring insulation worn through, allowing the signal wire to short against engine ground
• Blown fuse protecting the glow plug bus bar or control circuit
• Malfunctioning glow plug relay or PCM-controlled switching module
• Power supply wire to the cylinder 5 plug severed or disconnected
• Acid or moisture intrusion into the glow plug well causing stray conduction

How to diagnose P067C

1. Hook up a scan tool, verify P067C lives in the permanent memory, and record the freeze frame data — this captures engine load, coolant temperature, RPM, and vehicle speed at the moment of failure.
2. Pull all stored codes from every module. Related electrical faults or redundant glow plug codes often point toward the root cause rather than assuming cylinder 5 itself failed.
3. Perform a hands-on inspection of the entire glow plug wiring harness, focusing on the boot covering cylinder 5's connector. Look for cracked insulation, melted sheathing, greenish corrosion deposits, or loose terminal tension.
4. Check for battery voltage at the cylinder 5 connector reference terminal while the glow cycle is active — absence of voltage indicates a supply-side problem upstream.
5. Use a multimeter to measure resistance from the control circuit to chassis ground. Readings under one ohm confirm a direct short in the harness.
6. Test each glow plug individually for proper resistance using the manufacturer's specification (typically 0.5–2.0 ohms for healthy plugs). An open circuit reads infinite resistance.
7. Erase the code, perform a complete drive cycle including a cold soak and restart, then rescan to confirm P067C stays cleared rather than immediately returning.

Repair options and costs for P067C

Tackle the inexpensive possibilities before committing to major component replacement:

• Single glow plug replacement — parts run $25–$80, with one to two hours of labor at $75–$120 per hour, totaling roughly $80–$200
• Glow plug relay or control module swap — parts between $50–$200 plus one to two hours shop labor, landing around $150–$450 total
• Complete glow plug set replacement (all cylinders) — parts $150–$400 plus three to four hours labor, costing approximately $250–$600

Total cost to fix P067C

The final bill hinges entirely on which part failed. Most P067C diagnoses resolve around the $150–$300 range when the issue is a single bad plug or minor wiring damage. Full-set replacements push toward the higher end, especially on engines requiring intake manifold access for cylinder 5. Always perform the electrical verification steps before purchasing any components — misdiagnosis wastes money and leaves the original fault unresolved.

Can you drive with P067C?

The engine runs normally once warmed up, so P067C does not strand you immediately. The real danger surfaces on cold mornings: with cylinder 5 and potentially other plugs degraded, starting becomes difficult or impossible below freezing. Address this before winter arrives or before any extended cold-weather trip. Temporary fixes like block heaters buy time, but the underlying electrical fault will only worsen.