096 Transmission
ON BOARD DIAGNOSTIC, GENERAL INFORMATIONFunction
The 096 automatic transmission is controlled electro-hydraulically. "On Board Diagnostic" (OBD) capability refers specifically to the electrical and electronic controls.
The Transmission Control Module (TCM) -J217- receives input signals from components that effect gear selection, and sends output signals to solenoid valves that control gear selection in the valve body.
The TCM is equipped with Diagnostic Trouble Code (DTC) Memory so that, in the event of an electrical/electronic component malfunction or an open circuit, the cause of the malfunction can be determined quickly.
Malfunctions in the monitored sensors or components are stored in DTC Memory along with an indication of the type of malfunction.
Malfunctions that occur only occasionally are defined as "sporadic" malfunctions and are coded as such.
The Transmission Control Module analyzes the information and distinguishes different types of malfunctions. Those that do not reoccur within 5 to 20 km (3 to 12 miles) or 6 to 24 minutes are stored as sporadic malfunctions.
Electrical malfunctions that affect vehicle performance can be identified using the VAG 1551 Scan Tool (ST). The On Board Diagnostic capabilities can only be fully exploited using operating mode 1 ("Rapid data transfer").
Safety functions of the Transmission Control Module
If critical malfunctions occur while driving, the transmission will continue to operate in an emergency running mode. If a malfunction occurs while the selector lever is in position "D," "3", or "2", the 3rd gear emergency running mode is activated.
If a malfunction occurs while the selector lever is in position "1", "P", "N", or "R" the emergency running mode for that stage is activated.
If the engine is started again in the emergency running mode and the malfunction occurs when the selector lever is in position "D", "3", or "2", then 3rd gear is activated hydraulically, until the malfunction is repaired.
If there are malfunctions that result in emergency running, the transmission remains in the emergency running mode until the ignition is switched OFF.
Malfunctions that may activate emergency running mode
Open circuit in wiring, short-circuit, malfunctions in electrical or hydraulic components.
Transmission Control Module recognition of malfunctions
If a malfunction exists for a certain time, it is stored as a static malfunction. A malfunction that is recognized but does not occur again within a certain time or distance is stored as a "sporadic malfunction."
Malfunctions that are stored in DTC Memory as sporadic malfunctions will be displayed as such when retrieved by the VAG 1551 Scan Tool. In such cases, the letters "SP" appear on the right side of the Scan Tool display. If the printer is switched on, "sporadic DTC" is printed out after the malfunction is addressed.
Malfunctions that are stored in DTC Memory as sporadic malfunctions are automatically erased after 1,000 km (600 miles) or 20 hours.