The DME control unit is equipped with a self diagnostic program that will detect emissions related malfunctions and turn the CHECK ENGINE light ON while the engine is running. Emissions related fault codes stored in the DME control unit can be read by activating the program and counting the flashes of the CHECK ENGINE light on the instrument panel. Fault codes stored in all other control units are only accessible with the BMW Service Tester that connects to the diagnostic connector in the engine compartment. The tester is menu driven and will provide operation instructions on the screen.
In the DME control unit, fault codes provide information about which circuit or component is malfunctioning at the time of the test. Intermittent malfunctions are also stored as an existing fault. As useful as these codes are, the first step in repair or service to engine management systems is to gain as much information as possible about the vehicle, especially regarding intermittent problems. Also check any service records which may be available. Before repairing any reported faults, it is absolutely essential to check for any obvious mechanical faults or failures. Remember, a fault code only indicates which sensor or circuit is effected by the problem. Simple mechanical faults such as a vacuum leak, bad battery or poor electrical connection can cause a fault code.
The fault code memory will be erased anytime the battery or DME control unit is disconnected. Fault codes will also be erased after the engine is started 60 times with no additional failures.
- All DME codes are 4 digits. The first digit will always be 1 .
- With the ignition switch ON and the engine not running, press the accelerator pedal to the floor 5 times in less than 5 seconds. This will close the full load switch to activate the diagnostic program. If the program will not activate, the full load switch on the throttle body or accelerator pedal sensor is not working.
- The CHECK ENGINE light will stay ON for 5 seconds, then flash once, then begin flashing the first fault code.
- The light will flash once for 1 ; twice for 2 , etc. Each digit will be flashed with about 2.5 seconds between digits. When the whole code has been displayed, the light will stay ON for 2.5 seconds, then start on the next code, if existent. Count the flashes and write the numbers down.
- If the first code is 1444, no faults are stored in memory.