Function

On Board Diagnostic (OBD), function
The automatic transmission is controlled electro-hydraulically.
The Transmission Control Module (TCM) -J217- is supplied with information from components which influence gear selection, and generates signals to control the relevant solenoid valves in the valve body. The solenoid valves direct the fluid pressure produced by the ATF pump to actuate the appropriate clutches or brakes in the transmission.

Transmission control module -J217- fault recognition
The term "On Board Diagnostic (OBD)" relates specifically to the electrical and electronic part of the control system.
The control module is equipped with a (DTC) memory so that in the event of an electronic/electrical component failure or on open circuit the fault can be determined quickly. Faults are recognized by electrical signals and stored in the DTC memory together with an indication of the type of fault and fault location.
The control module recognizes faults during vehicle operation and stores them in a (DTC) memory. This information will remain available even if the system voltage fails.
The control module distinguishes between faults present (permanent) and temporary faults (sporadic).
If a fault is no longer present after a certain period or a lengthy drive, it will be converted to a sporadic (SP) (DTC).
A fault will also be converted to sporadic when the DTC memory is not erased after repairs.
Faults that are stored in the memory as sporadically occurring faults, will be displayed as "sporadic DTCs" when checked by the scan tool VAG 1551. In such cases "SP" appears on the right of the display. If the printer is switched on, the print-out will show "sporadic DTC" after the identification of the fault.
If the sporadic DTC does not occur again after 40 cold engine starts (and subsequent transmission warm-up), the fault in (DTC) memory will be automatically erased.
The possibilities offered by On Board Diagnosis can only be fully utilized with the vehicle diagnostic, testing and information system VAS5051 or the VAG1551 scan tool (mode 1, rapid data transfer).
Available functions of vehicle diagnostic, testing and information system VAS5051 or the VAG1551 scan tool.

Security functions of the Transmission Control Module (TCM)
When one or more components or sensors fail, the Transmission Control Module (TCM) - J217- activates the appropriate replacement functions or emergency programs. This ensures destruction-free operation of the automatic transmission with some effect on the function and quality of shifting.
When critical malfunctions occur with an active transmission control module -J217-, the currently selected gear will be held. "Mechanical emergency running mode with the control module active" is activated by the transmission control module -J217- as soon as the driving situation regarding transmission security and engine security permits it.

Mechanical backup with active control module
^ The transmission shifts out of all forward gears into 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 of the segments of the transmission range selector lever display are lit up completely.
^ The MIL lights up after 2 Dcy); check DTC memory and compare with DTC table.
If the TCM -J217- malfunctions (e.g. if the power supply is faulty or the connector becomes disconnected), the transmission will immediately switch to "mechanical back-up mode with inactive control module" and continue to operate.

Mechanical backup with non-active control module
^ The transmission shifts out of all forward gears into 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 of the segments of the transmission range selector lever display are dark.
^ The MIL lights up when the Engine Control Module (ECM) has recognized a CAN-bus malfunction (missing data exchange between engine and transmission control modules) (after 2 Dcy); if necessary, check DTC memory of the control module.
^ Transmission control module -J217- does not function at all, i.e. it cannot be checked via On Board Diagnostic (OBD).