"SERVICE ENGINE SOON (MIL) - IHKA FC 8013A3. The malfunction indictor lamp (MIL) illuminates at start-up or during trip. Heating function is usually working properly. Fault code 8013A3 "" Electric auxiliary heater (high voltage): OBD temperature sensor, coolant below operating range"" is stored in the fault memory of the IHKA control unit. IHKA control unit software."