P0672
Cylinder 2 Glow Plug Circuit
When a vehicle powertrain module registers the fault code P0672, it points directly to an internal system malfunction identified as "Cylinder 2 Glow Plug Circuit". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
P0672 is triggered when the PCM detects an abnormal condition associated with cylinder 2 glow plug circuit. You may notice diesel engine misfires on cold start, white exhaust smoke, all of which are direct consequences of this malfunction. Low severity — the car drives normally, but the fault should be diagnosed and resolved within the next few weeks.
Symptoms
Diesel engine misfires on cold start, white exhaust smoke
Common Causes
- Failed cylinder 2 glow plug
- Broken wire to cylinder 2 glow plug
- Loose glow plug nut/connector
- Bad glow plug relay
How to Fix
- 1 Test glow plug resistance and replace
- 2 Repair broken wiring
- 3 Tighten electrical connections
- 4 Replace glow plug relay
Technical Explanation
To set P0672, the PCM samples the affected circuit multiple times per second, comparing live readings against manufacturer-programmed operating windows. A two-trip detection strategy is employed for most powertrain codes: the fault must be detected on one drive cycle, the vehicle key-cycled off, and the fault detected again on the next drive cycle before the MIL illuminates and a permanent DTC is stored. Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
Immediate safety risk is low with P0672 active. The primary concern is regulatory — this fault will cause a failed emissions test — and the secondary risk is that the small root cause (failed cylinder 2 glow plug) becomes a larger problem if ignored for months.
Mechanic's Pro Tip
Before replacing any component on P0672, spend 5 minutes inspecting the wiring harness and connector first — corrosion, chafed insulation, and backed-out pins cause the majority of these faults and cost nothing to fix. Use a multimeter to measure voltage drop across the connector pins under load; anything above 0.1V indicates excessive resistance that will cause intermittent failures even after replacing the sensor.
Glow plug replacement: $80 - $200