OBD-II Code
P0670
Severity
Not yet reviewed
Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.
Can you drive it
We cannot say
Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.
Indicative cost (USD)
$120–$1,400
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
P0670 sets when the PCM loses communication or detects an electrical fault on the glow plug control module circuit, meaning the engine computer cannot command or verify glow plug operation.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then follow the diagnostic notes further down this page, in the order they are written.
They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
Read the full diagnostic procedureP0670 sets when the PCM loses communication or detects an electrical fault on the glow plug control module circuit, meaning the engine computer canno…
P0670 sets when the PCM loses communication or detects an electrical fault on the glow plug control module circuit, meaning the engine computer cannot command or verify glow plug operation.
Start cheapest
this is a diesel-only code and cold-start hard-start complaints are the customer-facing symptom, so confirm hard-start before tearing into electrical diagnosis. Scan-tool check the glow plug module commanded state versus actual current draw if your tool supports it (typical glow plug current is 15 to 25 amps per plug on a 12V system during the pre-heat cycle), and verify battery voltage at the module's main power feed; a corroded power feed or melted fusible link is the cheap fix here. On platforms with a separate FICM or GPCM, check the ground straps and the small-gauge control wire from PCM to module; a single broken control wire mimics a failed module. Caveat: replacing all eight glow plugs and the harness on a P0670 without first verifying the module's power, ground, and PCM command signal is a $600 to $1,400 mistake.
Vehicle-specific patterns2003 to 2007 Ford 6.0L Powerstroke is the textbook P0670 vehicle, where the FICM and the GPCM both sit on the passenger valve cover and suffer water…
- 2003to 2007 Ford 6.0L Powerstroke is the textbook P0670 vehicle, where the FICM and the GPCM both sit on the passenger valve cover and suffer water ingress from the cowl drain, corroding the connectors.
- 2008to 2010 Ford 6.4L Powerstroke shares the same pattern with the dual-relay glow plug control.
- 2003to 2009 Dodge Ram with the 5.9L and 6.7L Cummins uses a grid heater rather than glow plugs, but the grid heater relay sets P0670 when its terminals corrode.
- 2001to 2010 GM 6.6L Duramax LB7/LLY/LBZ trips P0670 when one or more 12V glow plugs short to the head and pull the module into protection mode.
Estimated repair$120 to $1,400.
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