OBD-II Code
P0674
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)
$80–$2,800
From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
$80 (single plug, accessible) to $2,800 (broken-off tip extraction on the LML).
P0674 means the ECU detected a fault in the glow plug circuit feeding cylinder 3 specifically — open, short, or resistance out of spec per the Glow Plug Control Module's per-cylinder current monitor.
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 procedureP0674 means the ECU detected a fault in the glow plug circuit feeding cylinder 3 specifically — open, short, or resistance out of spec per the Glow P…
P0674 means the ECU detected a fault in the glow plug circuit feeding cylinder 3 specifically — open, short, or resistance out of spec per the Glow Plug Control Module's per-cylinder current monitor.
The cheapest-first diagnostic ladder
- Disconnect the glow plug pigtail at cylinder 3 and ohm the plug at the terminal — healthy reading is 0.4-2.0 ohms cold (most plugs land 0.6-1.2 ohms); 0 ohms is a dead-shorted plug, infinite is an open/burned filament, and 4+ ohms is a weak plug on its way out and is the leading cause of hard cold-start complaints on diesels with no DTC at all.
- Verify the GPCM PWM command on the scan tool — duty cycle 0-100% scaled to coolant temp, glow-on time 5-30 sec; if the GPCM is commanding 0% on cylinder 3 only, the module logic has flagged the circuit as faulted and locked it out.
- Clamp an amp probe on the cyl 3 feed wire and confirm 7-20A initial inrush falling to 5-15A as the plug heats; 0A with command ON is an open in the harness or a burned plug. Test resistance INDIVIDUALLY at the glow plug terminal — pulling a shorted plug measures 0 ohms; an open plug measures infinite; a marginally weak plug measures 4+ ohms cold and is the most common cold-start hard-start root cause. Replace as a set on diesel engines — mixed-age plugs cause progressive failure.
Vehicle-specific patterns2008-2010 Ford 6.4L Powerstroke V8 throws P0674 from cylinder 3 (driver's bank, second from front) when the under-valve-cover glow plug harness chafe…
- 2008-2010Ford 6.4L Powerstroke V8 throws P0674 from cylinder 3 (driver's bank, second from front) when the under-valve-cover glow plug harness chafes against the rocker assembly — Ford issued multiple service bulletins on the 6.4 UVCH (under-valve-cover harness); cylinder 3 is one of the most-replaced positions because of its proximity to the EGR plumbing.
- 2011-2016Duramax LML/LGH 6.6 V8 throws P0674 from a known glow plug failure mode where the tip swells and either breaks off into the cylinder (catastrophic) or seizes in the head — GM TSB territory; if the plug won't unscrew at 30 ft-lb, stop and soak with penetrant for 24 hr before twisting it off.
- 2007-2018Cummins 6.7 inline-6 throws P0674 on cylinder 3 (mid-block, the hottest position thermally) more often than any other cylinder.
- 2009-2014Mercedes Sprinter OM642 V6 throws P0674 when one bank's glow plug harness gets pulled tight during turbo or EGR service.
Estimated repair$80 (single plug, accessible) to $2,800 (broken-off tip extraction on the LML).
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