Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This means there's a problem with the part of the car that controls how much fuel goes into the engine for cylinder number 7. It's like a switch that isn't working right.
The code indicates that the electrical circuit controlling the fuel injector for cylinder 7 is reading a higher voltage than expected.
P31A1 is an OBD-II diagnostic trouble code indicating an issue with the low side circuit of the hydrogen injector for cylinder 7. The circuit is experiencing higher voltage levels, which could be due to wiring issues, a faulty injector, or a problem with the engine control module (ECM).
• Engine misfire
• Reduced engine performance
• Check engine light illuminated
• Faulty injector
• Wiring issues or shorts in the circuit
• Malfunctioning engine control module (ECM)
Injector: A device that sprays fuel into the engine's combustion chamber.
ECM: Engine Control Module, the computer that controls engine functions.
• Check the wiring and connections for cylinder 7 injector.
• Test the injector for proper operation.
• Inspect the ECM for faults.
• Repair or replace damaged wiring.
• Replace the faulty injector.
• Reprogram or replace the ECM if necessary.
• Multimeter
• OBD-II scanner
• Wiring repair kit
$200 - $800
Moderate
• Toyota Mirai
• Hyundai Nexo
• Honda Clarity Fuel Cell
• Regular maintenance of the fuel system
• Inspect wiring harnesses periodically
• Use quality fuel to prevent injector clogging
Engine Performance
• Avoid driving the vehicle until repaired to prevent further damage.
• Consult a professional mechanic for accurate diagnosis.
Check with the vehicle manufacturer for warranty coverage on fuel system components.
This code is relatively rare and specific to vehicles using hydrogen fuel systems.
High – Immediate attention is required to prevent engine damage.
Driving with this issue can lead to increased emissions and potential safety risks.
• Engine at operating temperature
• Vehicle in a safe, stationary position
The injector for cylinder 7 is located on the engine block, typically under the intake manifold.
Q: Can I drive my car with a P31A1 code?
A: It's not recommended, as driving with this code can cause engine damage.
Q: How do I clear a P31A1 code?
A: After repairs, use an OBD-II scanner to clear the code, but ensure the issue is resolved first.
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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.