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 fuel injector for cylinder 5 in your car's engine. It's like a tiny nozzle that sprays fuel, and it's not working right because it's getting too much power.
The engine control module (ECM) has detected a high voltage condition in the high-pressure injector circuit for cylinder 5.
The P31C9 code indicates that the high side circuit for the high-pressure fuel injector in cylinder 5 is experiencing higher than normal voltage. This can be due to a short circuit, faulty wiring, or a malfunctioning injector.
• Check Engine Light is on
• Engine misfires or runs rough
• Reduced engine performance
• Faulty fuel injector in cylinder 5
• Short circuit in the injector wiring
• Faulty ECM or control module
Injector: A device that sprays fuel into the engine's combustion chamber.
ECM: Engine Control Module, the computer that controls engine functions.
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for cylinder 5's injector.
• Test the injector for proper operation.
• Replace the faulty injector.
• Repair or replace damaged wiring.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$200 - $500
Moderate
• BMW 3 Series
• Audi A4
• Mercedes-Benz C-Class
• Regular maintenance and inspection of fuel system components.
• Ensure proper electrical connections.
• Use high-quality fuel to prevent injector clogging.
Engine Performance
• Have a professional diagnose and repair the issue.
• Avoid driving the vehicle until the problem is fixed to prevent further damage.
Check with the vehicle manufacturer for warranty coverage on engine components.
This code has been associated with high-performance vehicles with direct fuel injection systems.
Moderate – Should be addressed soon to avoid engine damage.
Driving with a misfiring engine can lead to increased emissions and potential safety hazards.
• Engine at operating temperature
• Vehicle running under load
The fuel injector for cylinder 5 is located on the engine, typically near the intake manifold.
Q: Can I drive with a P31C9 code?
A: It's not recommended to drive with this code as it can cause engine damage.
Q: How can I prevent injector issues?
A: Regular maintenance and using high-quality fuel can help prevent injector problems.
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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.