A/T Controls - Failsafe Mode/Code 4F8D Stored

SI B 24 04 07
Automatic Transmission

April 2007
Technical Service

SUBJECT
ZF 6HP19TU in Fail-safe Mode with Fault 4F8D Stored

MODEL
E90, E91, E92 with N52K or N54 engines and the 6HP19TU automatic transmission produced from 9/01/06 up to 2/28/2007

SITUATION

The transmission goes into fail-safe mode with fault code 4F8D (ratio monitoring, gearshift 5-4 plausibility) stored in the EGS.

CAUSE

EGS software diagnostics is too sensitive.

This fault may occur during a 5-4 downshift only in vehicles with either low mileage, a replacement transmission, or after a reset of the adaptation values.

CORRECTION

On a customer complaint basis only, perform an adaptation run as described in the procedure below.

Note:
The transmission adaptation occurs only at a transmission oil temperature of 75°C or higher. Once a transmission oil temperature of 75°C is reached, carry out the adaptation run as follows:

1. In drive position "D", increase vehicle speed up to 4th gear (approximately 25 mph), but do not allow a shift into 5th gear.

2. Allow the vehicle to then coast to a stop and keep the vehicle stationary for approximately 15 seconds with the brake pedal applied.

3. Next, with the vehicle stationary, change from D to N and back to D again.

4. Repeat steps 1 to 3 approximately 10 times.

This problem is solved in series production beginning 3/01/07 with integration level E89x-07-03-510.





WARRANTY INFORMATION

Covered under the terms of the BMW New Vehicle Limited Warranty.





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