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). RETRIEVING CODES (APPROVED METHOD) Turn ignition switch to the "2" position. After 3 seconds, the malfunction light will start flashing fault codes. One flash for fault code 1, two flashes for fault code 2, three flashes for fault code 3 or four times for fault code 4. If more than one fault code is present, malfunction light will flash fault codes in order of occurrence. After the first fault code is flashed, the malfunction light will be off for 3 seconds. If any other fault (s) are present, malfunction light will flash code related to fault. After all fault codes are flashed, malfunction light will be off for 3 seconds and then remain on until ignition key is turned off. This signals the end of fault codes present. If malfunction light stays on continuously, after 3 seconds with ignition switch in "2" position, fault codes 1-4 are not present. This does not mean, however, that other trouble codes may be stored in memory. TROUBLE CODE IDENTIFICATION NOTE: Using malfunction light for self-diagnosis is not a substitute for the BMW System Tester. Diagnosis is only available for fault codes 1-4. Trouble codes listed in TROUBLE CODE IDENTIFICATION TABLE, are only found when using the BMW System Tester. Page 1 of 1 2/5/2010 ...All malfunction codes are stored in MCU memory. Stored malfunction codes are displayed without the BMW diagnostic module by turning the ignition switch to RUN position and depressing accelerator 5 times to wide open throttle (WOT) within 5 seconds. See DIAGNOSTIC FLASH CODES table. If a malfunction is detected on any of the components listed, it will cause diagnostic system to illuminate CHECK ENGINE light. CLEARING CODES When repairs have been completed, malfunction light will go out. To clear trouble codes from memory, start, stop and restart engine 5 times. If BMW System Tester is available, trouble codes can be cleared by performing (999). An optional method is to turn ignition off, disconnect negative battery cable and reconnect cable. If malfunction light is still on or flickers, other faults are present. Complete testing can only be performed with the BMW System Tester. If no hard fault codes are present and vehicle starts, proceed to TESTS W/O CODES article for diagnosis by symptom (i.e. ROUGH IDLE, NO START, etc.) or intermittent diagnosis procedures. TROUBLE CODE DIAGNOSIS MALFUNCTION LIGHT NOT ON/NO START Fuel Pump Relay Ensure fuel pump fuse No. 23 is okay. Turn ignition switch to RUN position. Disconnect fuel pump relay (in control box at right or left shock tower). Perform voltage tests at relay connector as indicated in FUEL PUMP RELAY TESTS table. Correct any problems found. If all voltages are as specified, go to MCU POWER & GROUND test.
CAUTION: Disconnecting negative battery cable may also erase all pre- selected settings for radio, seat memory, trip computer, etc.
If you do the gas pedal method post all four digit codes and I will tell you what they are.
Friday, February 5th, 2010 AT 1:52 PM