Common reasons for the OBD to illuminate include oxygen sensor failure; malfunctioning catalytic converter, spark plug and ignition coil failures; EGR vale malfunction etc. When the engine light comes on it is best not to drive your vehicle where possible. If you are a RAC member with Roadside assistance, we suggest calling RAC to arrange a Patrol to attend to your vehicle to ensure it’s safe to drive. Or you can bring your vehicle into one of our 10 Auto Service Centres where our trained Technicians will investigate the issue. (RAC members are entitled to one 30 mins free diagnoses every 12 months and will save 10% on labour for any repairs required).