General Information

Group 24
Automatic Transmission

Bulletin Number
24 03 93 (3763)

Woodcliff Lake, NJ
April 1993
Product Engineering

SUBJECT:
Updated Transmission Control Module EPROM

MODELS:
740iA/iL

Complaint:
"Trans Program" displayed on the instrument cluster matrix display AND fault code 100 or 105 stored in the transmission control module.

or

Harsh 1-2 upshift and what some customers may describe as an excessive amount of gear changes, both up and down.

Cause:
Due to normal production tolerances in the transmission, each clutch has slightly different fill times and friction characteristics. The parameters on the original transmission control module EPROM may not allow the control unit sufficient time to adapt to the individual transmission's characteristics before logging a fault.

Correction:
An updated EPROM is available for the transmission control module which will solve the above complaints. Control modules which already have the updated EPROM may be identified by calling up the Identification page of the transmission control module using the BMW Service Tester or MoDiC and checking the control module Serial Number; Serial Number C2729X or greater identifies the control module as having the latest EPROM.

The transmission control module must be left disconnected from the wiring harness for at least 60 minutes after exchanging the EPROM as this will ensure that any previously stored adaptation values are erased. As the amount of time required for adaptation to occur has been increased, please be advised that installation of the EPROM and a quick trip around the block will most likely not be sufficient to provide a proper evaluation of the new software. In exceptional cases, depending on the number of shifts, it may be necessary to accumulate 50-100 miles of driving for proper evaluation of the new software.

TRANSMISSION CONTROL MODULE

EPROM Exchange Instructions

Preparatory Instructions:
The installation of the updated EPROM into the Transmission Control Module is a simple procedure.

However, before beginning the EPROM exchange, the following conditions must be provided and the designated tools must be used.

ENVIRONMENT

The work area where the EPROM is exchanged must be free of excessive dust and aggressive chemicals or vapors. A small uncarpeted office within the dealership is recommended. Since low atmospheric humidity promotes static electricity, an evaporating bowl of water can be used to raise the humidity level of the work area.

EQUIPMENT

Screwdrivers (blade type) are only used to open and close the Control Module. The EPROM is exchanged using an IC extractor/inserter set. Tool sets can be obtained locally (Radio Shack, Archer # 276-1581).

STATIC ELECTRICITY

The Transmission Control Module can be damaged and rendered unusable by static electrical discharge. For this reason the 3M static protection kit (or equivalent) must be used during the entire EPROM exchange procedure. See S.I. 04 30 87 (1546) for complete details.

EPROM STORAGE

Replacement EPROMs must be stored in the original shipment containers. The label in the center of the EPROM must never be removed.