OBD diagnostics: what the car tells about itself

Since 2001 every petrol and since 2004 every diesel in the EU has an OBD-II port (under the wheel). A €10–30 Bluetooth ELM327 + app (Torque, Car Scanner) reads codes, shows live data and clears the check-engine light. Codes: P0xxx engine, B body, C chassis, U network. Important: a code is a symptom, not a diagnosis — “lambda lean” can be sensor, vacuum leak or fuel pump.

• ●Flashing check engine = misfires, cat at risk — ease off, workshop
• ●Screenshot codes BEFORE the workshop — don’t get sold “replace everything”
• ●Clearing kills the lamp, not the cause: it returns