Entering Self-Diagnostics

If the malfunction light stays on or flickers while driving, a malfunction exists in one of the on-board computers. These computers include the Motronic Control Unit (MCU), Trip Computer, Climate Control Computer, Electronic Transmission Control Unit and Anti-Theft System.

BMW requires a special BMW System Tester to access all self-diagnostic trouble codes. The BMW System Tester can access the memory from all computers. It can display malfunctions, perform output solenoid and relay activation tests, etc.

The MCU will indicate faults in the following driveability related circuits; airflow meter, Oxygen (O2) control system, engine temperature sensors and throttle position switch. The MCU can store up to 5 fault codes at once.

The BMW System Tester must be used to display trouble codes. These consists of 2 digit codes. See TROUBLE CODE IDENTIFICATION TABLE for list of available codes. This article includes diagnosis for trouble codes (found on BMW System Tester) and fault codes (malfunction light on dash).