Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with the little heater in the engine that helps start the car when it's cold. It's like when a toaster doesn't heat up because something is wrong with the wires.
The engine control module (ECM) has detected a low voltage or resistance issue in the glow plug control circuit for cylinder 3.
The P066E code indicates that the ECM has found a low voltage condition in the glow plug control circuit for cylinder 3. Glow plugs are used in diesel engines to preheat the combustion chamber, ensuring efficient starting and operation in cold conditions. A low circuit condition can be caused by a faulty glow plug, wiring issues, or a malfunctioning control module.
• Difficulty starting the engine, especially in cold weather
• Engine misfires or runs rough
• Check Engine Light is illuminated
• Faulty glow plug in cylinder 3
• Damaged or corroded wiring or connectors
• Malfunctioning glow plug control module
Glow Plug: A device used to preheat the air in a diesel engine to aid in starting.
ECM: Engine Control Module, the computer that controls engine functions.
• Scan the vehicle for additional trouble codes.
• Inspect the wiring and connectors for damage or corrosion.
• Test the glow plug in cylinder 3 for proper resistance.
• Replace the faulty glow plug.
• Repair or replace damaged wiring or connectors.
• Replace the glow plug control module if necessary.
• OBD-II scanner
• Multimeter
• Socket set
$100 - $300
Moderate
• Ford F-250
• Chevrolet Silverado 2500
• Dodge Ram 2500
• Regularly inspect and maintain glow plugs.
• Keep electrical connections clean and free of corrosion.
• Perform routine engine diagnostics.
Sensor Issue
• Have the vehicle inspected by a professional if the Check Engine Light is on.
• Avoid driving the vehicle in extremely cold conditions until repaired.
Check with the vehicle manufacturer for specific warranty coverage on engine components.
Glow plug issues have been common in diesel engines, especially in older models or those frequently used in cold climates.
Moderate – It is advisable to address this issue soon to avoid starting problems and potential engine damage.
Driving with a malfunctioning glow plug can lead to increased emissions and potential engine damage.
• Cold engine start
• Normal operating temperature
The glow plug for cylinder 3 is typically located on the engine block, near the third cylinder.
Q: Can I drive with a P066E code?
A: It's best to get it fixed soon, as it can lead to starting problems and increased emissions.
Q: How do I know if a glow plug is bad?
A: Symptoms include difficulty starting the engine, especially in cold weather, and a rough running engine.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
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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.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.
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.
View options on Amazon
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.