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 car that helps inject fuel into cylinder number 12. It's like a broken wire or switch that isn't letting fuel get in properly.
The engine control module (ECM) has detected a problem with the electrical circuit that controls the fuel injector for cylinder 12. This could be due to a break or open circuit.
The P31AE code indicates that the ECM has identified an open or malfunction in the low side circuit of the hydrogen injector for cylinder 12. This can affect the fuel delivery to the cylinder, impacting engine performance.
• Check Engine Light is on
• Engine misfire
• Poor engine performance
• Faulty injector
• Open or shorted wiring harness
• Poor electrical connection in the injector circuit
ECM: Engine Control Module
Injector: A device that delivers fuel into the engine's cylinders
• Use an OBD-II scanner to confirm the code.
• Inspect the wiring and connectors for cylinder 12 injector.
• Test the injector for proper operation.
• Repair or replace damaged wiring or connectors.
• Replace the faulty injector.
• Clear the code and test drive the vehicle to ensure the issue is resolved.
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• BMW 7 Series
• Mercedes-Benz S-Class
• Audi A8
• Regular maintenance checks
• Ensure proper fuel quality
• Inspect wiring harnesses periodically
Engine Performance
• Do not ignore the Check Engine Light.
• Have the vehicle inspected by a professional if unsure.
Check with your vehicle manufacturer for warranty coverage on injectors.
This code has been associated with vehicles using advanced fuel injection systems, particularly in luxury models.
Moderate – It should be addressed soon to prevent further engine performance issues.
Ignoring this issue may lead to increased emissions and potential engine damage.
• Engine running
• Vehicle at operating temperature
The injector for cylinder 12 is located on the engine, typically on the side where cylinder 12 is positioned.
Q: Can I drive my car with this code?
A: It's not recommended to drive for long periods with this issue as it can lead to engine damage.
Q: Will this code cause my car to fail an emissions test?
A: Yes, a malfunctioning injector can cause increased emissions, which may result in a failed test.
High-End · Full-system diagnostics
A full-system bidirectional platform aimed at advanced DIY users and professional diagnostic workflows.
Network faults often require full-system access instead of a generic code reader alone.
View on Amazon
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.
View on Amazon
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.
View on AmazonThese are optional diagnostic tools, not guaranteed fixes. As an Amazon Associate I earn from qualifying purchases.
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.
View options on Amazon
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.