Car Problems

OBD2 error code dictionary: what P0300, P0420, P0171 and P0299 mean, common causes and what to check before the workshop.

10guides~8min fix

Learn the OBD2 code structure in five minutes: P/B/C/U codes, SAE code families, the most common codes and the correct reading method.

P0300 meaning, 6 likely causes and the right check order: plug-coil swap test, vacuum leak detection, MAF and fuel pressure checks.

P0420 meaning and the right diagnostic order: exhaust leak, O2 sensor, mixture codes and catalyst test — think about the expensive part last.

P0171 meaning and the right check order: MAF cleaning, vacuum leak, fuel pressure and O2 checks — go from cheap to expensive.

P0401 meaning and an EGR cleaning guide: carbon build-up, actuator, sensor and cooler checks step by step, plus when to replace the valve.

P0299 underboost meaning and check order: intercooler hose leaks, DPF clogging, wastegate actuator and turbo checks step by step.

P0011 meaning and check order: oil maintenance, VVT solenoid cleaning, phaser and chain checks — go from cheap to mechanical.

P0087 meaning and a common rail pressure guide: fuel filter, return flow test, regulator and pump checks step by step.

Check engine light meaning: steady vs flashing difference, the 7 most common causes, code reading order and when to stop immediately.

The color logic of dashboard lights and the most critical ones: red-yellow-green split, the stop rule for oil and temperature, ABS-ESP-TPMS meanings.