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 is having trouble reading signals from a sensor that checks how well one of the engine's cylinders is working.
The ion current sense circuit monitors the combustion quality in the cylinder by measuring ionization currents. If the circuit detects an abnormal range or performance, it triggers the P2891 code.
The P2891 code is set when the powertrain control module (PCM) detects an issue with the ion current sense circuit for cylinder 1. This circuit is responsible for monitoring the ionization current, which is used to assess combustion quality and efficiency. A deviation from expected parameters can indicate a problem with the circuit or the combustion process itself.
• Check Engine Light is on
• Poor engine performance
• Increased fuel consumption
• Faulty ion current sensor
• Wiring issues such as shorts or opens in the circuit
• Malfunctioning PCM
PCM: Powertrain Control Module
Ionization: A process where atoms or molecules gain or lose electrons
• Use an OBD-II scanner to confirm the P2891 code.
• Inspect the ion current sensor and its wiring for damage.
• Test the circuit for continuity and proper voltage.
• Replace the faulty ion current sensor.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the PCM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Vehicle 1
• Vehicle 2
• Vehicle 3
• Regularly inspect engine sensors and wiring.
• Perform routine engine maintenance.
• Use high-quality fuel.
Sensor Issue
• Regularly check for engine warning lights.
• Have your car serviced at recommended intervals.
Check with your vehicle manufacturer for specific warranty coverage related to engine sensors.
The P2891 code has been associated with vehicles using advanced combustion monitoring systems, which have become more common in modern engines.
Moderate – It is advisable to address this issue soon to avoid potential engine performance problems.
Driving with an active Check Engine Light may lead to unsafe driving conditions and could result in further damage to the vehicle.
• Engine at operating temperature
• Vehicle in a safe and controlled environment
The ion current sensor is typically located near the ignition coils or integrated within the spark plug assembly.
Q: What happens if I ignore the P2891 code?
A: Ignoring this code can lead to poor engine performance and increased fuel consumption.
Q: Can I drive with the P2891 code?
A: While you may be able to drive, it's best to have the issue checked to avoid further problems.
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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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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.