P0671 code meaning
Cylinder 1 Glow Plug Circuit/Open
Powertrain system Generic code P06xx codes Check engine light
What P0671 means
Modern diesel glow systems switch each glow plug through its own power semiconductor (in a glow plug module or the engine module), so current and faults can be measured per plug; a faulty channel is switched off. CARB requires glow plugs to be checked for correct current and voltage drop and, since model year 2010, a single plug outside specification to be detected and named. P0671 means the load circuit of the cylinder 1 glow plug is open while glowing. Thresholds: GM engine-module drivers 200 kΩ or more (two trips), GM's L5P glow module less than 4.0 A at over 6 V, Ford's 2023 Power Stroke less than 1 A for about 1 s. Older GM systems (LB7/LLY, LML) report open and short under this one code. Chrysler advises checking the main B+ feed and ground of the glow module first when several cylinder codes appear together.
P0671 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P0671
- Check engine light (GM also glow plug lamp)
- Harder cold start in low temperatures
- Rough idle, knocking and white or blue smoke after a cold start
- Often no symptoms when warm
Common causes of P0671
- Most likelyGlow plug cylinder 1 burnt out (element open)
- PossiblePlug connector loose or corroded, terminal nut loose, wire broken
- PossibleGlow module supply or ground (several cylinder codes at once)
- Less likelyGlow module or driver faulty, or software (GM 3.0 L 2020)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Glow plugGlow plug wiringGlow plug control module
What each part of P0671 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 71 | The exact fault in that area. |
What to do next
- Note P0671 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0671
What does P0671 mean?
P0671 means "Cylinder 1 Glow Plug Circuit/Open". Modern diesel glow systems switch each glow plug through its own power semiconductor (in a glow plug module or the engine module), so current and faults can be measured per plug; a faulty channel is switched off. It is a generic code, so it means the same on every make.
Is it safe to drive with P0671?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0671 fail an emissions test?
Yes, it can. P0671 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0671 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0671 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.