Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer found a problem with the part that helps heat up the engine when it's cold. It's like when a toaster doesn't get hot enough to toast bread.
The P066C code indicates that the control circuit for the glow plug in cylinder 2 is experiencing low voltage, which means it might not be working properly.
The glow plug control circuit for cylinder 2 is not receiving the correct voltage. This could be due to a faulty glow plug, wiring issues, or problems with the control module. Glow plugs are used in diesel engines to preheat the combustion chamber, aiding in starting the engine, especially in cold conditions.
• Difficulty starting the engine
• Engine misfires
• Increased exhaust smoke
• Faulty glow plug
• Damaged wiring or connectors
• Faulty glow plug control module
Glow Plug: A device used in diesel engines to preheat the air in the combustion chamber to aid starting.
Control Circuit: The electrical circuit that manages the operation of a component.
• Check for any other related codes.
• Inspect the glow plug and wiring for damage.
• Test the voltage at the glow plug connector.
• Replace the faulty glow plug.
• Repair or replace damaged wiring or connectors.
• Replace the glow plug control module if necessary.
• Digital multimeter
• Socket set
• Wiring diagram
$100 - $300
Moderate
• Ford F-250
• Chevrolet Silverado
• Ram 2500
• Regularly inspect glow plugs and wiring.
• Use high-quality fuel to prevent deposits.
• Perform regular engine maintenance.
Engine Performance
• Have the vehicle inspected by a professional.
• Do not ignore the check engine light.
• Ensure regular maintenance is up to date.
Check with the vehicle manufacturer for warranty coverage on engine components.
Glow plug issues are common in diesel engines, especially in colder climates where they are used more frequently.
Moderate – Addressing this issue promptly can prevent further engine starting problems.
Driving with malfunctioning glow plugs can lead to increased emissions and potential engine damage.
• Engine cold start
• Ambient temperature below 40°F
The glow plug is located in the cylinder head of the engine, near the fuel injector for cylinder 2.
Q: Can I drive with a P066C code?
A: It's not recommended to drive for extended periods as it can lead to starting issues and increased emissions.
Q: How can I prevent glow plug issues?
A: Regular maintenance and using high-quality diesel fuel can help prevent glow plug issues.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Commonly relevant for misfire, ignition-efficiency, and some drivability-related repairs.
Misfire and ignition-related faults commonly involve spark plugs as part of the repair path.
Check the correct plug type, gap, and engine application for your vehicle.
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Fitment Required · Vehicle-fitment part
Relevant when the fault points toward ignition-coil performance or cylinder-specific ignition issues.
Some ignition faults involve coil performance or cylinder-specific coil problems.
Match the coil to your engine and confirm the failed component before ordering.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.