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 part of the engine that puts fuel into cylinder 1. It's not getting enough power to work properly.
The engine control module (ECM) has detected a low voltage condition in the high side circuit of the high-pressure injector for cylinder 1.
The P31C0 code indicates that the ECM has found a low voltage in the high side circuit of the high-pressure fuel injector for cylinder 1. This can affect the injector's ability to properly deliver fuel to the cylinder, impacting engine performance.
• Engine misfires
• Poor fuel economy
• Check Engine Light on
• Faulty injector
• Wiring issues or poor connections
• Faulty ECM
Injector: A device that sprays fuel into the engine's cylinders.
ECM: Engine Control Module, the computer that controls the engine.
• Check for any other related codes.
• Inspect the injector and wiring for damage.
• Test the voltage and continuity of the injector circuit.
• Replace the faulty injector.
• Repair or replace damaged wiring or connectors.
• Reprogram or replace the ECM if necessary.
• Multimeter
• OBD-II scanner
• Basic hand tools
$200 - $600
Moderate
• Toyota Prius
• Honda Insight
• Chevrolet Volt
• Regular maintenance checks
• Ensure good quality fuel is used
• Inspect wiring regularly
Engine Performance
• Do not ignore the Check Engine Light.
• Seek professional diagnosis if unsure.
• Keep up with regular vehicle maintenance.
Check with your vehicle manufacturer for warranty coverage on injectors.
This code has been more prevalent in hybrid vehicles due to their complex fuel delivery systems.
Moderate – Should be addressed soon to prevent further engine issues.
Driving with a misfiring engine can lead to increased emissions and potential damage to the catalytic converter.
• Engine running
• Vehicle at operating temperature
The injector for cylinder 1 is located on the engine, typically near the intake manifold.
Q: Can I drive with a P31C0 code?
A: It's not recommended to drive for long with this code, as it can lead to more severe engine issues.
Q: How can I reset the Check Engine Light?
A: After fixing the issue, you can use an OBD-II scanner to clear the code and reset the light.
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.