Search common fault codes by vehicle make, control unit and engine system. Exact meanings and checks can vary by model, year and manufacturer.
These are general OBD-II descriptions. The exact definition, test procedure and likely repair can differ by model, engine and software. Confirm the code and live data on the vehicle before replacing parts.
The control unit detects less exhaust gas recirculation flow than expected.
Check EGR readings and control, then inspect the valve, passages, sensors and wiring. Do not replace parts based on the code alone.
The monitoring system evaluates catalyst efficiency below its threshold.
Check for leaks, misfires, fuel trims and sensor operation first. Assess the catalyst after related causes are ruled out.
The controller detects reduced particulate filter efficiency; this code applies to specific diesel configurations.
Check differential pressure, sensors, regeneration history and causes of excess soot. The repair depends on the model and the filter’s actual condition.
The system detected SCR efficiency below expectation; exact logic varies by manufacturer.
Use diagnostic equipment to check dosing, fluid quality, NOx sensors, exhaust sealing and SCR readings.
Measured boost is below the requested value under certain engine conditions.
Compare requested and actual boost, then check intake sealing, turbo control, vacuum and sensors. P0299 alone does not confirm that the turbo must be replaced.
Boost pressure exceeded the limit specified by the engine calibration.
Check the sensor, control hoses and actuator movement. If power drops or limp mode occurs, reduce load and arrange diagnostics.
Fuel trims indicate excess air or insufficient fuel for cylinder bank 1.
Check intake sealing, fuel pressure, MAF readings and fuel trims at different operating conditions.
Fuel pressure is below expectation; checks depend on the fuel system and operating conditions.
Compare requested and actual pressure, then check supply, filter, pump and sensor using the procedure for that engine.
Measured mass air flow does not match expected engine parameters.
Inspect the intake and filter, verify MAF signal and power, then compare readings with engine load.
The controller detected more exhaust gas recirculation flow than expected.
Compare commanded and measured EGR values; inspect sealing, the valve, sensors and connectors.
The diesel controller estimated particulate filter loading above its threshold.
Check differential pressure and regeneration history, then trace excess soot production. Do not force regeneration before checking the required conditions.
The controller detected a boost-system deviation; this code alone does not confirm a failed turbocharger.
Compare requested and actual boost, then inspect system sealing, vacuum/control and sensor signals.
The turbo control position sensor signal is outside the expected range.
Check sensor power and signal, actuator travel and mechanism movement using the procedure for that engine.
Fuel trims indicate excess fuel or insufficient air for cylinder bank 1.
Check short- and long-term fuel trims, fuel pressure, airflow and injector sealing.
Fuel pressure feedback does not match the expected value for the operating condition.
Compare commanded and actual pressure; check sensor power and fuel delivery using the procedure for that engine.
The control unit receives a lower-than-expected MAF signal.
Check MAF power, ground and signal, the connector and intake tract. Do not replace the sensor without measurements.
The MAP signal does not match engine load and speed.
Compare MAP readings with ignition on and with the engine running; inspect intake, sensor power and wiring.
The engine warms up more slowly than expected or does not reach its target temperature.
Compare displayed and actual temperature from cold start to warm-up; inspect the thermostat and sensor.
The controller detected a fault in the upstream oxygen sensor circuit.
Check the signal trace, heater and wiring; rule out exhaust leaks and mixture faults before replacing the sensor.
The controller detected misfires in one or more cylinders.
Review cylinder misfire counters and conditions; check ignition, fuel delivery, intake and compression.
The controller detected a combustion misfire in cylinder 1.
Compare cylinder counters, check ignition and injector operation, then compression and leakage. Confirm cylinder numbering for the engine.
The controller detected a combustion misfire in cylinder 2.
Check misfire counters, ignition and injector operation, then compression. Cylinder numbering varies by engine.
The controller is not receiving the expected crankshaft position signal.
Check the waveform, power, connector, wiring and tone wheel using the engine-specific service information.
The controller detected a fault in the camshaft position sensor signal.
Compare crankshaft and camshaft signals; check power and wiring, then inspect mechanical valve timing.
The ABS module detects a circuit or signal issue at the left front wheel.
Compare live wheel speeds and inspect the signal, harness, encoder and hub. Confirm any suffix/subcode for the make.
The ABS module detects a circuit or signal issue at the right front wheel.
Compare all four wheel speeds and inspect the signal, harness and encoder. Check the manufacturer procedure and subcode.
The ABS module detected a circuit/signal issue at the left rear wheel.
Review live wheel speeds and the sensor waveform; inspect the harness and encoder for the rear hub design.
The ABS module detected a circuit/signal issue at the right rear wheel.
Compare the wheel speed with the others, check the wiring and signal, then inspect the encoder and hub.
B0010 is associated with restraint-system diagnostics, but the exact circuit and definition are assigned by the vehicle maker.
Read the complete code and subcode with a compatible scan tool. Leave pyrotechnic restraint circuit diagnosis to a trained technician; do not probe with a test lamp.
Without the make, model, year and full subcode, B0011 cannot be assigned reliably to a specific restraint component.
Confirm the exact definition from the VIN and full subcode, then follow the manufacturer procedure. Do not clear the code without resolving the cause.
A code stored by the engine controller usually reports a request from the transmission module; the underlying fault is in the TCU data.
Scan the TCU directly and review its companion codes and data. P0700 alone does not mean the transmission needs replacement.
The transmission controller detected an input-speed sensor signal fault.
Compare input and output speed data, check the circuit and vehicle-specific service information, and rule out communication faults first.
The transmission controller detects a mismatch between expected and measured gear ratio.
Review speed data and companion codes; check fluid level and condition using the maker procedure. Avoid loading a slipping transmission.
The transmission controller detected a torque-converter lock-up deviation.
Compare lock-up command and slip, then check fluid and hydraulics using the transmission-specific procedure.
The transmission controller receives an incorrect or missing output-speed signal.
Check live output speed, sensor power and waveform, wiring and the tone wheel.
A control unit is not receiving ECM/PCM messages over the data network.
Scan all modules and check power, grounds and network condition. Do not replace the engine controller based on U0100 alone.
Another controller is not receiving TCU messages over the vehicle network.
Check whether the TCU responds to a scan, verify power and network communication, and review codes in other modules.
One or more controllers are not receiving messages from the braking system module.
Check ABS-ECU access, power, grounds and network lines. If ABS/ESP warnings are active, account for reduced safety functions.
Try another code or filter.
A Check Engine code is a clue. Our team can check fault memory, live data, wiring and related systems to find what is behind it.