Glow Plug Heater Circuit (Cylinder 5) Malfunction
The engine control module (ECM) has detected a problem with the glow plug for cylinder 5.
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What it means (plain English)
The computer found an issue with the heating element that helps start the engine in cold weather for cylinder 5, making it harder to start or run smoothly.
What the computer is actually seeing
The ECM monitors the voltage across the glow plug circuit. For a working glow plug, you should see around 10-12 volts while it is active. If the voltage drops significantly or shows an open circuit, it triggers this code.
What a healthy reading looks like
Glow plug voltage should be around 10-12 volts when active; resistance should typically be less than 5 ohms for a good glow plug.
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. Check the glow plug circuit wiring and connectors for damage or corrosion. If damaged, repair or replace as necessary. Decision: Good condition or damage found?
- 22. Using a multimeter, check the resistance of the cylinder 5 glow plug. Expected resistance is less than 5 ohms. Decision: Resistance under 5 ohms or higher?
- 33. If resistance is high, replace the glow plug and recheck for the code. Decision: Code returns or does not return?
- 44. If resistance is normal, check the voltage at the glow plug while starting the engine. Should be 10-12 volts. Decision: Voltage OK or low?
- 55. If voltage is low, check the glow plug relay operation and wiring from the relay to the glow plug. Replace the relay if faulty. Decision: Relay works or does not work?
Common causes
- Faulty glow plug
- Bad electrical connection or wiring issue
- Failed glow plug relay
- Faulty ECM
- Corroded connectors
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable but starting may be difficult in cold weather. Recommend fixing soon.
Will this code come back after replacing the glow plug?
If the glow plug is the only issue and replaced, it shouldn't come back unless there's another underlying issue.
Why does this code appear with others?
It may show alongside codes for other cylinders if multiple glow plugs or the wiring circuit is experiencing issues.
Working a real vehicle right now?
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