Brakes - Erroneous ABS Fault Internal Defect

9215bmw01

Group 34
Brakes


Bulletin Number
34 05 91 (3418)


Woodcliff Lake, NJ
January 1992
Product Engineering


This Service Information Bulletin supercedes S.I. 34 05 91 (3418), dated November, 1991. It incorporates revised model information.

Please remove and discard S.I. 34 05 91, dated November 1991 from your S.I. Binder.

SUBJECT: Microprocessor Controlled ABS (uC-ABS) Stores Erroneous "Internal Defect" Fault


MODELS: 7 Series (E32) - Vehicles produced 06/91 and later, equipped with M30 engine 5 Series (E34) - Vehicles produced 9/91 and later


Situation: An increasing number of uC-ABS control units are being returned under warranty for having shown "internal defect" during troubleshooting and readout of the fault memory. In most of these cases, the fault is erroneous.

Cause: If the ignition is switched on with the cap of the D100 diagnostic connector removed, a low voltage condition on the TxD lead to this control unit can set the above-mentioned erroneous fault.

Correction: If this fault is encountered proceed as follows:

1. While the diagnostic module is still connected and the ignition is switched on, erase the fault in the uC-ABS fault memory.

2. Switch OFF the ignition before disconnecting the diagnostic cable.

3. Reconnect the cap for the D100 diagnostic connector, before the ignition is switched ON again.


4. Do not replace control unit

Note: This condition will not affect the operation of the uC-ABS system, and the customer will not notice the condition, as the ABS warning light will be switched OFF when the diagnostic connector cap is reconnected (unless a genuine fault is detected).


The uC-ABS control unit is being modified to prevent this condition. The method of identifying the modified uC-ABS control units will be published in a future Service lnformation bulletin.

Warranty
Status: Information only.