On-Board Diagnostic (OBD), Function

On-Board Diagnostic (OBD), function, 09G, 6 Spd. A/T
The automatic transmission is controlled electro-hydraulically.

On-Board Diagnostic (OBD) or "self-diagnosis" is specifically for the electronic/electric control of the transmission.

Functions of transmission control module
The control module receives information from components that effect selection of gears and passes the information on to solenoid valves that control the valves in the valve body.

In the dynamic shift program the control module adapts itself to the existing driving resistance (e.g. gradients, trailer) as well as to the driver's driving style (e.g. sporty driving style) and selects the corresponding shift points.

The control module is equipped with a Diagnostic Trouble Code (DTC) memory so that in the event of an electronic/electrical component failure or on open circuit the DTC can be determined quickly. DTCs are recognized by electrical signals and stored in the DTC memory.

Transmission control module fault recognition
The control module detects malfunctions while driving and stores them in the DTC memory go to DTC table. Transmission Control Systems

This information is also kept when there is no battery voltage.

The control module distinguishes between permanent and sporadic malfunctions.

If the malfunction does not occur within a predetermined time or distance again, the fault is stored as a sporadic malfunction.

A malfunction also becomes a sporadic malfunction when the DTC memory has not been erased after a repair.

DTCs which are stored in the memory as sporadically occurring, will be displayed as "sporadic faults" when retrieved by the VAS 5051 tester. "SP" appears on the right of the display in such cases. If the printer is switched on, "sporadic faults" are printed out after the fault is addressed.

If the malfunction does not occur within a predetermined time or distance again the DTC is erased in the memory.

Safety functions of transmission control module
If malfunctions occur when driving, the control module can activate functions or emergency running modes. These could have effects on the gear function and quality.





All segments of the selector lever position display in the instrument cluster will light-up when the control module is functioning and when the transmission is in emergency running mode.

The selector lever position display will show nothing when the control module is faulty and the transmission is in emergency running mode.

The transmission will remain in emergency running mode; until the fault is no longer recognized by the control module over a predetermined period.