Reading and Clearing Diagnostic Trouble Codes

In the event of a DME system malfunction, circuit information will be stored in the internal memory of the DME control unit. Intermittent failures are stored with a record of the failure frequency. The DME control unit is able to store up to five malfunctions, and will give priority to those items which can cause the vehicle to exceed exhaust emission standards. In addition to being stored in memory, an emissions-related failure will cause the "Check Engine" light to illuminate on the instrument cluster. Furthermore, the "Check Engine" light is used to display faults which are stored in the control unit's memory when the self-diagnostic procedure is initiated. Faults may also be retrieved with the BMW service tester if available.


All troubleshooting should begin by "checking the basics". Certain basic faults can be undetectable by the self-diagnostic system of the DME control unit and in some cases can actually interfere with the self-checking and fault memory operation. Refer to "CHECKING THE BASICS".



ENTERING SELF-DIAGNOSTICS

1. Switch the ignition to the run (ON) position.
2. Depress the accelerator pedal five (5) times to the wide open throttle position within five (5) seconds.
3. Read and record any flash codes that are displayed.
4. Refer to the "FAULT CODE CHART" for the affected component or system.
5. Proceed with the diagnosis procedures as outlined in "COMPONENT TESTING".
6. Repair or replace the affected component or system.
7. Clear the fault code.

Fig. 4 "Check Engine" Light Code Display:

^ tR = 5 sec. preparation for read-out
^ tWS = 0.5 sec. wait for synchronization
^ t1 = 2.5 sec. additional check engine lamp check
^ t2 = 2.5 sec. wait for read-out
^ t3 = 0.5 sec. check engine lamp on
^ t4 = 0.5 sec. check engine lamp off
^ t5 = 2.5 sec. time between code digits
^ t6 = 2.5 sec. time between different codes

CLEARING FAULT CODES

The fault code memory may be cleared by one of the following methods:

^ The BMW service tester.
^ Disconnect the subject control unit (ignition OFF).
^ Disconnect the vehicle battery.
^ The engine is started 50 times after repair of the failure.