P0670 — Glow Plug Control Module Circuit — 6.7 Powerstroke
P0670 on 6.7 Powerstroke means the PCM has detected a fault in the glow-plug control module circuit. This affects glow plugs and cold start. Typical on this…
What it means
The PCM has detected a fault in the glow-plug control module circuit.1
Most likely causes
- Glow-plug control module failure — Module internal fault or communication loss with PCM.1
- Wiring/harness damage to the glow-plug control module circuit — Chafed, corroded, or open wiring between PCM and control module or to glow plugs.1
- Individual glow plug or its circuit fault — Open/shorted glow plug or connector issue can trigger module circuit code.1
How to diagnose
- Verify code and freeze frame for ambient temperature and engine runtime.
- Inspect glow-plug control module connectors and harness for corrosion, chafing, or moisture.
- Check module power and ground supplies per wiring diagram; look for opens/shorts.
- Perform module self-test/communication check with scan tool to confirm PCM sees module.
- Inspect glow plug circuits for opens/shorts and measure resistance to ground per service spec.
- Clear code and monitor readiness after repairs; confirm cold-start performance.
Specs and test values
| Check | Normal reading | When to measure | Source |
|---|---|---|---|
| Battery and charging voltage | 12.6–12.7 V at rest when fully charged; about 13.5 V running | Engine off, then running with loads on | DieselHub |
| Glow plug resistance | Low — usually no more than about 6 Ω — and similar on every plug; an open reading means a failed plug | Engine off, meter lead to engine ground | DENSO |
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
- Scan tool with diesel/Powerstroke diagnostics
- Digital multimeter
- Wiring diagram for 6.7 Powerstroke glow system
- Inspection light
- Dielectric grease
Tools you’ll need
- OBD-II scan tool — Reads P0670 and freeze frame to confirm ambient temperature and engine runtime conditions for the glow-plug control module fault.
- digital multimeter — Checks module power, ground, and wiring continuity for opens/shorts in the glow-plug control module circuit.
- glow plug resistance tester — Measures individual glow plug resistance to ground to identify a faulty plug or circuit contributing to the module fault.
- inspection mirror and flashlight — Allows visual inspection of the glow-plug control module connectors and harness for corrosion, chafing, or moisture.
Rough cost and difficulty
| Likely repair | Parts | Shop labor | Who usually does it |
|---|---|---|---|
| Wiring or connector repair | $10–$100 | 1–4 hrs | DIY with tools and a manual |
| Glow plugs (full set) | $80–$250 | 2–6 hrs | DIY with tools and a manual |
| Glow plug relay or control module | $60–$400 | 0.5–2 hrs | Easy DIY |
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 diagnosis requires high-pressure fuel system access, internal engine work, or PCM reprogramming, have a qualified diesel technician perform the work. Stop if you are unsure; incorrect repairs can cause no-start or cold-start 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
Repair videos: P0670 on the 6.7 Power Stroke
Third-party videos, not ours — picked for this engine. Confirm anything against the factory service information for your truck.
Spotted an error, or something missing? Tell us
Run a 6.7 Powerstroke? This goes straight to the editor — it is not published.