P0671 — Cylinder 1 Glow Plug Circuit — 6.0 Power Stroke

P0671 diagnostic reference for 6.0L Power Stroke (2003.5–2007).

Updated October 15, 2026

What it means

P0671 is the generic OBD-II code for Cylinder 1 Glow Plug Circuit. On the 6.0L Power Stroke the glow plugs are run by a frame-mounted Glow Plug Control Module (GPCM) which reports per-cylinder circuit faults P0671–P0678. The code means the GPCM has detected an open or fault in the cylinder 1 glow plug circuit.¹

Most likely causes

1. Burned-out cylinder 1 glow plug — The glow plug element has failed open, so the GPCM sees an open circuit on cylinder 1. Typical on this platform for P0671.¹
2. Corroded or damaged GPCM connector / wiring — The GPCM sits on the frame rail and is exposed to moisture and road salt; corrosion or water intrusion at the GPCM connector can cause a per-cylinder circuit fault and communication issues.²
3. GPCM power/ground or control circuit fault — Loss of power, ground, or the PCM-to-GPCM command circuit can cause glow-plug circuit reporting errors. Check GPCM power and ground and the PCM-to-GPCM wiring.³
4. Glow plug harness/connector fault at cylinder 1 — On the 6.0L the glow plug circuit wiring runs to the cylinder head area; chafing, corrosion, or connector damage can open the cylinder 1 circuit.¹

How to diagnose

1. Verify the code and freeze-frame; confirm hard cold start/white smoke symptoms consistent with glow plug operation.
2. Inspect the frame-mounted GPCM connector for corrosion, moisture, or damaged pins; repair connector and wiring as needed.
3. Check GPCM power and ground feeds and the PCM-to-GPCM control circuit for continuity and corrosion.
4. Perform a resistance/continuity check of the cylinder 1 glow plug circuit from the GPCM to the glow plug connector; look for opens, high resistance, or chafed wiring.
5. If the circuit is intact, test the cylinder 1 glow plug resistance to ground; an open or out-of-spec reading indicates a failed glow plug.

Specs and test values

Common mistake to avoid

Replacing glow plugs or the glow module before checking the batteries. The glow system draws heavily, and low battery voltage causes circuit faults that no part swap will fix. Source: FleetRabbit — P0670 glow plug control module fault.

Parts and tools you may need

• Digital multimeter
• Wiring diagram for 6.0L Power Stroke GPCM circuits
• Dielectric grease
• Contact cleaner

Tools you’ll need

• digital multimeter — Measures glow plug resistance to ground and checks continuity/open in the cylinder 1 circuit from the GPCM to the plug.
• OBD-II scan tool — Reads and clears P0671 and freeze-frame data to confirm the fault and monitor GPCM-reported glow plug circuit status.
• terminal release tool set — Allows safe inspection and reseating of the frame-mounted GPCM and glow plug harness connectors without damaging pins.
• inspection mirror and LED flashlight — Provides clear view of the frame-mounted GPCM connector and wiring for corrosion, moisture, or chafing in tight underbody locations.

Rough cost and difficulty

Typical US independent-shop figures; labor runs about $120–$180 per hour (dealers charge more). Confirm the diagnosis before buying parts.

When to see a pro

If the GPCM is suspected failed, or wiring repairs are needed in the engine bay/frame rail, have a qualified diesel technician diagnose and repair to avoid misdiagnosis and further damage.

Check for recalls

Recalls are tied to your truck’s VIN, so check yours directly: enter the VIN at NHTSA’s recall lookup. Open safety recalls are repaired free at a dealer.

Sources