Glow Plug (G4) Circuit Open / Short to Ground
There’s an issue in the glow plug circuit for cylinder 4.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The glow plug for cylinder 4 isn't getting power or has a bad connection, affecting starting in cold weather.
What the computer is actually seeing
The engine control module (ECM) sees that the voltage from the glow plug circuit for cylinder 4 is out of range, either too low or too high, indicating a potential open or short in the circuit.
What a healthy reading looks like
Glow plug should have approximately 1 to 2 ohms resistance when measured cold, and the voltage should be around 12V when powered on.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the glow plug wiring harness for obvious damage or disconnections. If any issues are found, repair and retest the code.
- 22. Check the resistance of the glow plug for cylinder 4 with a multimeter. It should read between 1 to 2 ohms. If it's open (infinite resistance), replace the glow plug.
- 33. Verify the power supply to the glow plug circuit by checking the voltage with the ignition on. You should see approximately 12V at the connector. If not, check for blown fuses or wiring issues.
- 44. If the glow plug and wiring are good, inspect the engine control module (ECM) functions for faults. Use a scan tool to check for related codes and perform any functional tests.
Common causes
- Faulty glow plug for cylinder 4
- Bad wiring or connectors in the glow plug circuit
- Faulty engine control module (ECM)
- Blown fuse related to the glow plug system
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive my vehicle with this code?
You can drive it, but starting may be tough in cold conditions. Fix it soon for reliable operation.
Will the code come back after fixing?
If the underlying issue is properly addressed (like replacing faulty parts and fixing connections), it shouldn’t come back.
Why does this code show up with others like P0671?
They may indicate problems with the glow plugs in different cylinders; it's common for multiple cylinders to fail due to similar issues.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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