Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means there's a problem with the car's computer trying to switch between different fuel modes for one side of the engine. It's like when you try to change TV channels, but the remote isn't working right.
The engine control module (ECM) is detecting a high voltage issue in the circuit responsible for switching fuel modes in Bank 2 of the engine.
P31F3 indicates that the ECM has detected a higher than expected voltage in the switchover fuel mode circuit for Bank 2. This could be due to a short circuit, open circuit, or a malfunctioning component within the high-pressure fuel system.
• Check Engine Light is on
• Poor fuel efficiency
• Engine misfires or runs rough
• Faulty high-pressure fuel injector
• Wiring issues such as shorts or opens in the circuit
• Malfunctioning ECM
ECM: Engine Control Module
Bank 2: The side of the engine opposite to Bank 1, typically on V-type engines
• Perform a visual inspection of the wiring and connectors for damage.
• Use a multimeter to check for voltage and continuity in the circuit.
• Test the high-pressure fuel injector for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the faulty high-pressure fuel injector.
• Reprogram or replace the ECM if necessary.
• OBD-II scanner
• Multimeter
• Basic hand tools
$200 - $1000
Moderate
• Vehicle 1
• Vehicle 2
• Vehicle 3
• Regular maintenance of the fuel system
• Ensure proper wiring connections
• Use quality fuel to prevent injector issues
Engine Performance
• Avoid driving the vehicle until the issue is resolved to prevent further damage.
• Consult a professional mechanic for accurate diagnosis and repair.
Check with the vehicle manufacturer for warranty coverage on ECM and fuel system components.
This code is relatively uncommon and typically associated with vehicles that have advanced fuel management systems.
High – This issue can lead to poor engine performance and should be addressed promptly.
Ignoring this code may lead to increased emissions and potential safety risks.
• Engine running
• Vehicle at operating temperature
The high-pressure injector and related wiring are located on the engine, typically on the cylinder head of Bank 2.
Q: Can I drive with a P31F3 code?
A: It's not recommended to drive with this code as it can lead to further engine damage.
Q: How do I reset the P31F3 code?
A: After repairs, use an OBD-II scanner to clear the code, but ensure the issue is fixed first.
High-End · Full-system diagnostics
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Network faults often require full-system access instead of a generic code reader alone.
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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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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.