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 there's a problem with the electrical wiring or connection for the fuel injector in the first cylinder of the engine. It's like a light bulb not turning on because the wire is broken or disconnected.
The engine control module (ECM) has detected an issue with the electrical circuit for the injector in cylinder 1. This could be due to an open circuit or a faulty connection.
The P21CF code indicates that the ECM has detected an open circuit or a disconnection in the injector circuit for cylinder 1. This can prevent the injector from delivering fuel properly, affecting engine performance.
• Engine misfire
• Poor fuel economy
• Check Engine Light is on
• Faulty fuel injector
• Open or shorted injector wiring
• Poor electrical connection at the injector
ECM: Engine Control Module
Injector: A device that sprays fuel into the engine's cylinders
• Use a scan tool to verify the code.
• Inspect the wiring and connectors for damage or disconnection.
• Test the fuel injector for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the faulty fuel injector.
• Clear the code and test drive to ensure the issue is resolved.
• OBD-II scan tool
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Ford F-150
• Chevrolet Silverado
• Toyota Camry
• Regularly inspect and maintain engine wiring.
• Use quality fuel to prevent injector clogging.
• Perform regular engine tune-ups.
Engine Performance
• Do not ignore the Check Engine Light.
• Seek professional assistance if unsure about repairs.
Check if the vehicle's warranty covers fuel injector issues.
This code has been associated with injector circuit issues in vehicles with electronic fuel injection systems.
Moderate – should be addressed soon to prevent further engine performance issues.
Driving with a misfiring engine can lead to increased emissions and potential safety hazards.
• Engine running
• Vehicle at operating temperature
The fuel injector for cylinder 1 is located on the engine's intake manifold.
Q: Can I drive with a P21CF code?
A: It's not recommended as it can lead to poor engine performance and increased emissions.
Q: How do I reset the Check Engine Light after repair?
A: Use an OBD-II scan tool to clear the code, or disconnect the battery for a few minutes.
High-End · Full-system diagnostics
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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.