On-Board Diagnostic (OBD)

On Board Diagnostic (OBD)
The automatic transmission is controlled electronically and hydraulically.
The Transmission Control Module (TCM) -J217for the automatic transmission obtains information from components that have an effect on the shifting. Based on this information the TCM controls the respective solenoid valves in the valve body. The solenoid valves direct the oil pressure created by the ATF oil pump to the respective clutches or brakes.

Malfunction recognition by the Transmission Control Module (TCM)

The TCM is equipped with Diagnostic Trouble Code (DTC) memory. Malfunctions that occur in the monitored sensors, components, or wiring are stored in DTC memory, which can be checked using the VAS 5051 tester or VAG 1551 Scan Tool (ST). If the printer of the VAG 1551 scan tool is switched on, the DTC will be printed. DTC memory, checking.

The On Board Diagnostic (OBD) system differentiates between "static" and "sporadic" malfunctions. Static malfunctions are stored until DTC memory is checked and then erased using the VAS 5051 tester or VAG 1551 scan tool. If a malfunction that has been stored as "static" no longer exists after the ignition is switched on, it will be converted to "sporadic".

Malfunctions that occur sporadically are identified by the "/SP" designation in the VAS 5051 tester or VAG 1551 scan tool display. A sporadic malfunction is automatically erased after 40 transmission cold-starts and subsequent transmission warm-up. A warm-up cycle is recognized when the temperature is below 71°C at start and rises by at least 21°C.

The OBD program can be initiated using the VAS 5051 tester or VAG 1551 scan tool operating mode 1 "rapid data transfer'.
Functions that the scan tool is capable of overview of selectable functions

Transmission Control Module (TCM), backup functions
If one or more components or sensors malfunction, the TCM -J217- activates corresponding substitute functions or backup programs. This insures that the automatic transmission operates without damage or effect to the operation or quality of the shifting.
If certain malfunctions occur and the TCM is active, the transmission range engaged at that moment is maintained. As soon as the driving situation permits, the TCM activates the "mechanical backup with active control module" mode while ensuring transmission security.

Mechanical backup with active control module
^ The transmission shifts out of all forward gears into the hydraulic 4th gear. The torque converter clutch is unlocked (not applied). All solenoid valves are de-energized.
^ Maximum shift pressure is applied to the power transmitting elements.
^ Reverse gear an be engaged. The shift lock solenoid is active (in "P" and "N").





^ All of the segments in the transmission range selector lever display are lit up completely.
^ The Malfunction Indicator Lamp (MIL) is switched on after 3 driving cycles (dcy).
If the TCM malfunctions, for example if there is a power loss or a connector is disconnected, the transmission immediately operates in "mechanical backup with non-active control module" mode.

Mechanical backup with non-active control module
^ The transmission shifts out of all forward gears into the hydraulic 4th gear. The torque converter clutch is unlocked (not applied). All solenoid valves are de-energized.
^ Maximum shift pressure is applied to the power transmitting elements.
^ Reverse gear can be engaged. The shift lock solenoid is active (in "P" and "N").





^ All segments of the transmission range selector lever display are dark.
^ The Transmission Control Module (TCM) -J217- is completely inoperative, meaning that it cannot conduct its OBD program.
^ The Malfunction Indicator Lamp (MIL) lights up when the Engine Control Module (ECM) has recognized CAN-Bus malfunctions (missing data exchange between the ECM and TCM) after 2 driving cycles. If necessary check DTC memory.

Malfunction Indicator Lamp (MIL), function
If emission-influencing malfunctions are recognized by the TCM, the Malfunction Indicator Lamp (MIL) will be switched on.





Location of the MIL: Integrated in speedometer.

Note: When the MIL is switched on, it will either blink or light continuously. In either case, the DTC memory for the TCM must be checked.
^ MIL flashing: there is a malfunction that could damage the Three Way Catalytic Converter (TKC). In this case drive only with reduced power.
^ MIL continuously on: there is a malfunction that degrades emissions. Check DTC memory of the Engine Control Module (ECM) or the TCM.
^ If there is a driveability problem (customer complaint) and the MIL is not on, check the MIL function since malfunctions that do not immediately switch on the MIL can be stared.

MIL function check:
^ Switch on ignition: MIL must come on.
If the MIL does not come on when the ignition is switched on (with the engine not running) and if necessary, check wiring and replace lamp.
^ Start engine and let idle. The MIL must switch off after a few seconds.
^ If the MIL does not switch off after the engine was started, check DTC memory.

Conditions for recognizing a driving cycle (DCY)
^ A driving cycle (dcy) is considered complete when the ignition is switched on one time, the engine is started, the engine start is recognized by the control module and the ignition is switched off again.