P06C6 — Cylinder 2 Glow Plug Incorrect

OBD2 code P06C6 flags a problem with the diesel glow plug system (cylinder 2 glow plug incorrect). The car is usually drivable while you plan the repair. Common culprits: corroded glow plug connectors, faulty glow plug relay or control module, blown fuse in the glow plug circuit.

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK 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.

How to diagnose with an OBD scanner

Read the code and freeze frame Connect an OBD2 scanner, confirm P06C6 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the diesel glow plug system for damage, corrosion, chafing or poor contact.
Subsystem check Measure resistance of each glow plug — an open plug reads infinite resistance.
Subsystem check Check voltage at the glow plug rail during the pre-glow phase.
Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P06C6 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P06C6 (parts and labor, USD, independent shop rates): Replace a full set of glow plugs: $250–$600; Replace the glow plug relay/module: $150–$450; Replace one glow plug: $80–$200. Overall, fixing P06C6 usually costs between $80 and $600. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Is it safe to drive with P06C6?

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.

How much does it cost to fix P06C6?

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

What is the most common cause of P06C6?

The most common causes are: corroded glow plug connectors, faulty glow plug relay or control module, blown fuse in the glow plug circuit.

What does OBD2 code P06C6 mean?

Will P06C6 clear itself?

Sometimes P06C6 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.

When your OBD2 scanner pulls code P06C6, the engine control unit has detected that the glow plug circuit for cylinder 2 is behaving outside its expected parameters. The technical label reads "Cylinder 2 Glow Plug Incorrect," and it falls under the powertrain category since it involves engine management. Diesel engines rely on these small heating elements to warm the combustion chamber during cold starts, and the ECU watches that system closely.

Cylinder numbering depends on your engine layout. On inline engines, cylinder 1 is at the front belt end, with others counted in sequence. V-configuration engines number differently depending on the manufacturer, so consulting your specific firing-order diagram is essential. This matters because some cylinders sit harder to reach, which directly affects labor time and your final bill. The control module sets P06C6 after comparing live voltage and current readings against factory-calibrated thresholds, typically across multiple drive cycles. It also captures a freeze-frame snapshot showing RPM, engine load, coolant temperature, and vehicle speed the instant the fault occurs. Reviewing that data first often points you straight at the problem.

Symptoms

A P06C6 fault rarely hides. Watch for these signs:

Persistent check engine light on the dashboard
Whitish exhaust smoke during cold starts, signaling unburned fuel
Glow plug indicator lamp remaining illuminated after startup
Difficulty starting the engine, especially on cold mornings
Rough, uneven idle that smooths out once the engine reaches operating temperature

Common Causes

The most frequent culprits behind P06C6, listed from most to least likely:

Wiring or connector damage in the cylinder 2 glow plug circuit
Corrosion or oxidation buildup on the glow plug electrical connectors
A failed glow plug relay or control module
A blown fuse protecting the glow plug circuit
A burned-out glow plug on cylinder 2

How to Diagnose P06C6

Follow these steps in order to isolate the root cause:

Plug in an OBD2 scanner and confirm P06C6 is stored. Save the freeze-frame data immediately — this record shows exactly what conditions triggered the fault and guides your next moves.
Scan for any related diagnostic trouble codes. Accompanying codes often expose the true culprit, such as short circuits or module failures. While you're at it, search for technical service bulletins (TSB) tied to your make, model, and VIN through the manufacturer portal or nhtsa.gov — many glow plug issues have published factory fixes or software updates.
Physically examine the wiring harness and connectors serving the diesel glow plug system. Look for frayed wires, broken insulation, moisture intrusion, corrosion, loose terminals, or connectors that don't snap securely together.
Measure the resistance of each glow plug individually using a multimeter. A healthy plug shows a low resistance reading; an open or failed plug displays infinite resistance.
Verify voltage reaching the glow plug rail during the pre-glow phase with the key on and the system activated. No voltage points to an upstream electrical problem.
Clear the code, then drive through a complete cycle including the conditions captured in the freeze frame. If P06C6 returns, you have an active fault that needs physical repair, not just a one-time glitch.

Repair Options and Costs

Address the simplest and cheapest possibilities before committing to major expenses:

Single glow plug replacement (cylinder 2): $80–$200
Glow plug relay or control module replacement: $150–$450
Full glow plug set replacement (all cylinders): $250–$600

Labor rates at independent shops typically run $75–$125 per hour. Replacing one plug usually takes under an hour on accessible engines, while a full set or relay job may run 1–3 hours depending on the layout.

The total bill to resolve P06C6 typically lands between $80 and $600, depending entirely on which component is at fault. An accurate diagnosis before purchasing parts keeps you from overspending — the priciest scenario is almost never the first thing to check.

Can You Drive with P06C6?

Once the engine is running and up to temperature, the glow plug system becomes irrelevant, so short-distance driving on warm days is generally safe. The real concern emerges on cold mornings: with a dead plug on cylinder 2, the engine may struggle to start or refuse to start entirely. If winter is approaching or you live in a cold climate, schedule the repair before you're stranded. P06C6 is a short-term severity issue — deal with it before cold weather arrives.