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.
Low severity. Can I keep driving?You can keep driving, although cold starts will be harder. Avoid cranking the starter repeatedly on cold days.
Cylinder 1 is numbered according to the manufacturer: check your engine's manual before working on it.
Symptoms
- 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
Most likely causes
- Glow plug cylinder 1 burnt out (element open)
- Plug connector loose or corroded, terminal nut loose, wire broken
- Glow module supply or ground (several cylinder codes at once)
- Glow module or driver faulty, or software (GM 3.0 L 2020)
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P0671 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 6: Control modules and outputs
- 71: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0671?
You can keep driving, although cold starts will be harder. Avoid cranking the starter repeatedly on cold days.
What causes code P0671?
The most common causes are: glow plug cylinder 1 burnt out (element open); plug connector loose or corroded, terminal nut loose, wire broken; glow module supply or ground (several cylinder codes at once).
Related codes
- P066ACylinder 1 Glow Plug Control Circuit Low
- P066BCylinder 1 Glow Plug Control Circuit High
- P06B9Cylinder 1 Glow Plug Circuit Range/Performance
- P06C5Cylinder 1 Glow Plug Incorrect
- P0670Glow Plug Control Module 1 Control Circuit/Open
- P052FGlow Plug Control Module 1 System Voltage
Sources
- law.cornell.edu: 13 CCR 1968.2
- gsi.ext.gm.com: 25OBDG04A
- fordservicecontent.com: obd summary diesel 2023
- gsi.ext.gm.com: 18OBDG04 Engine Diagnostics
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.