Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means the car's computer is having trouble reading signals from a sensor that checks how well cylinder 4 in the engine is working.
The ion current sense circuit monitors combustion quality in the cylinder by measuring ionization current. A fault in this circuit can affect engine performance.
The P289C code indicates a malfunction in the ion current sense circuit for cylinder 4. This circuit is responsible for detecting ionization in the combustion chamber, which helps in monitoring the combustion process. A fault here can lead to incorrect readings and misfire detection.
• Check Engine Light (CEL) is on
• Engine misfires
• Poor fuel economy
• Faulty ion current sensor
• Damaged wiring or connectors
• ECU malfunction
Ionization: The process of adding or removing electrons from an atom or molecule.
ECU: Engine Control Unit, the computer that controls engine functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors to the ion current sensor.
• Test the ion current sensor for proper operation.
• Replace the ion current sensor.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ECU if necessary.
• OBD-II scanner
• Multimeter
• Wiring repair kit
$150 - $500
Moderate
• Toyota Camry
• Honda Accord
• Ford Fusion
• Regular maintenance checks
• Timely replacement of sensors
• Ensure proper wiring connections
Sensor Issue
• Do not ignore the Check Engine Light.
• Get the vehicle diagnosed by a professional.
• Avoid driving long distances until fixed.
Check with the manufacturer if the vehicle is still under warranty for potential coverage.
This code has been more prevalent in vehicles with advanced combustion monitoring systems.
Moderate – Should be addressed soon to prevent further engine issues.
Driving with this code may lead to increased emissions and potential engine damage.
• Engine at operating temperature
• Vehicle in idle or under load
The ion current sensor is typically located near the ignition coils on the engine.
Q: Can I drive with a P289C code?
A: It's not recommended to drive for long periods with this code as it can lead to engine misfires.
Q: How is the ion current sensor related to engine performance?
A: It helps monitor combustion quality, which is crucial for efficient engine operation.
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Universal · Digital multimeter
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Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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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.