About Trouble Codes

Data bus, 09A, 5 Spd. A/T
For more information on data bus:
go to Additional Information, System Overviews, Other Topics, CAN-BUS Operation
Advantages:
^ Rapid data transfer between the control modules
^ Less wiring in vehicle
The automatic transmission control module sends signals into the data bus and uses signals from it. It exchanges signals (information) with other control modules.

Examples of signals from data bus (sent by engine control module)
^ Accelerator pedal position (throttle valve position)
^ Kickdown
^ Engine speed
^ Engine torque

Examples of signals into data bus (used by engine control module)
^ Cruise control system
^ Ignition timing influences

In addition to the engine control module, other control modules exchange information via the data bus as well, as this example shows.

If the automatic transmission control module detects that signals are missing or faulty, the data bus itself, another system or a component of another system may be faulty.

Therefore, always perform OBD of affected control modules.

Safety functions of transmission control module
The automatic Transmission Control Module (TCM) -J217- 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.

Control module -J217- with driving situation gear changes (Fuzzy Logic)
Determining the driving situation and driving resistance dependent gear change point happens automatically.

Advantages:
^ Gear changes will be consumption orientated
^ Maximum engine output is always available
^ Individual adaptation of gear change points in all driving situations
^ Gear change points are infinitely variable

Gear change point variations for gradients
An additional gear change map automatically selects gear changes for gradients dependent upon accelerator pedal position and driving speed.
^ Gear change map for extreme uphill stretches is matched to engine output.
^ Gear change map for extreme downhill stretches is matched to the braking effect of the engine

Vehicles with diesel engine
When the vehicle is stationary and the engine is at idle with the brake pedal depressed, the control module shifts to neutral with the selector lever remaining in position D for more comfort.

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

The control module recognizes malfunctions during vehicle operation and stores them in a DTC memory.

After analyzing the information the control module distinguishes between sporadic malfunctions and malfunctions present at this moment (static) and stores these.

If the malfunction is not present for a predetermined time or when driving over a longer distance, it is no longer recognized and becomes a sporadic malfunction.

A malfunction is also changed to a sporadic malfunction when the DTC memory is not erased after repairs.

Malfunctions which are stored in the memory as sporadically occurring malfunctions, will be displayed as sporadic malfunctions when retrieved by the V.A.G 1551 Scan Tool. SP appears on the right of the display in such cases. If the printer is switched on, sporadic malfunctions are printed out after the malfunction is addressed.

If the sporadic malfunction is not present for a predetermined time or when driving over a longer distance, the malfunction is erased in the DTC memory.

Safety functions of transmission control module
If malfunctions occur while driving, the control module can activate supplementary functions or an emergency running program. These can affect the quality and function of the gear changes.

Depending on the seriousness of the malfunction, the engine control module can react by:

shifting dependent on engine speed

shifting with increased pressure (noticeable to the driver by jolts)

shifting after 4H

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

Malfunctions which may lead to emergency running:
Open circuit in wiring, short-circuit, electrical or hydraulic components faulty.

Wiring open circuit and/or data bus wiring short circuit.

Replacing control modules
If control modules are replaced, the system must be returned to the basic setting.

V.A.G 1551 Scan Tool and system tester VAS 5051

Electrical malfunctions that affect the vehicle performance can be determined with these devices.

Note: V.A.G 1551 Scan Took

^ From July 1997 a further number on the right next to the Diagnostic Trouble Code (DTC) will be displayed/printed-out when checking the DTC memory (up-to-date program card version of V.A.G 1551). This number indicates the type of malfunction, which is also shown again in text under the affected component.