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 injector for cylinder 4 in your car. It might be touching something it shouldn't, which can cause issues with how the engine runs.
The P31B4 code indicates that the high side of the injector circuit for cylinder 4 is shorted to the ignition coil circuit.
The P31B4 code is triggered when the Engine Control Module (ECM) detects that the high side of the injector circuit for cylinder 4 is shorted to the coil. This can cause improper fuel injection and ignition timing, leading to engine performance issues.
• Engine misfire
• Reduced engine performance
• Check Engine Light illuminated
• Faulty injector for cylinder 4
• Short circuit in the wiring harness
• Faulty ignition coil
Injector: A device that sprays fuel into an engine's combustion chamber.
Ignition Coil: A component that converts battery voltage into the high voltage needed to create an electric spark in the spark plugs.
• Perform a visual inspection of the wiring harness for damage or shorts.
• Test the injector for cylinder 4 for proper operation.
• Check the ignition coil for cylinder 4 for faults.
• Repair or replace damaged wiring harness.
• Replace faulty injector for cylinder 4.
• Replace faulty ignition coil.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $400
Moderate
• Toyota Camry
• Honda Accord
• Ford F-150
• Regularly inspect wiring harness for damage.
• Perform routine maintenance on injectors.
• Ensure proper ignition coil function.
Engine Performance
• Avoid driving the vehicle until the issue is resolved.
• Consult a professional mechanic for accurate diagnosis.
Check with your vehicle manufacturer for specific warranty coverage related to injectors and ignition components.
This code is relatively uncommon and typically associated with specific wiring or component failures.
High – This issue can lead to significant engine performance problems and should be addressed promptly.
Driving with this code can cause further engine damage and may not comply with emissions standards.
• Engine at operating temperature
• Vehicle in a safe and controlled environment
The injector for cylinder 4 is located on the engine, near the intake manifold.
Q: Can I drive with a P31B4 code?
A: It's not recommended to drive with this code as it can cause further engine damage.
Q: How do I know if my injector is faulty?
A: Symptoms of a faulty injector include engine misfires, poor performance, and increased fuel consumption.
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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.