Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
Your car's computer is having trouble reading signals from a sensor in cylinder 12, which helps it know if the engine is running smoothly.
The ion current sense circuit monitors the combustion process in the cylinder by detecting ions. This helps the engine control module (ECM) optimize ignition timing and detect misfires.
The P28BC code indicates that the ECM has detected a malfunction in the ion current sense circuit for cylinder 12. This circuit is responsible for measuring ionization currents during combustion, which helps the ECM adjust ignition timing and detect misfires. A fault in this circuit can lead to incorrect engine performance data.
• Check Engine Light on
• Poor engine performance
• Increased fuel consumption
• Faulty ion current sensor
• Wiring issues in the ion current sense circuit
• Malfunctioning ECM
ECM: Engine Control Module
OBD-II: On-Board Diagnostics, Second Generation
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connections for cylinder 12's ion current sensor.
• Test the ion current sensor for proper functionality.
• Replace the faulty ion current sensor.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$200 - $600
Moderate
• BMW 7 Series
• Mercedes-Benz S-Class
• Audi A8
• Regularly inspect engine sensors and wiring.
• Perform routine engine maintenance.
• Use high-quality fuel to prevent sensor damage.
Sensor Issue
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional mechanic.
• Avoid driving aggressively until the issue is resolved.
Check with your vehicle manufacturer for warranty coverage on engine sensors.
Ion current sensing technology has been used in high-performance engines to optimize combustion and detect misfires.
Moderate – Addressing this issue promptly can prevent further engine performance problems.
Driving with a malfunctioning sensor can lead to increased emissions and potential engine damage.
• Engine at operating temperature
• Vehicle stationary and in park
The ion current sensor for cylinder 12 is typically located near the spark plug of the 12th cylinder.
Q: What happens if I ignore this code?
A: Ignoring this code can lead to poor engine performance and increased fuel consumption.
Q: Can I drive my car with this code?
A: While the car may still be drivable, it's not recommended to drive for extended periods without addressing the issue.
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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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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.