clutch AUDI A6 1996 C5 / 2.G 01V Transmission OBD Functions Workshop Manual

01-1


On Board Diagnostic (OBD),
function
The automatic transmission is controlled electro-
hydraulically.
The automatic Transmission Control Module
(TMC) -J217- receives information from
components that effect the selection of gears. It
passes the information on to solenoid valves that
control the solenoid valves in the valve body. The
solenoid valves convey the fluid pressure
generated by the ATF pump to the appropriate
clutches and brakes to be engaged.

Transmission Control Module (TMC) -J217-
malfunction recognition
The term "On Board Diagnostic (OBD)" applies
specifically to the electronic/electric control.
The control module is equipped with a Diagnostic
Trouble Code (DTC) memory so in the event of
an electronic/electrical component failure or on
open circuit, the malfunction can be determined
quickly. Malfunctions are recognized by electrical
signals and stored in the DTC memory together
with an indication of the type of malfunction and
malfunction location.
The control module recognizes malfunctions
during vehicle operation and stores them in a
DTC memory. This information will remain
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01-3

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 alternate 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
TCM, the current selected gear will be held.
"Mechanical emergency running mode with the
control module active" is activated by the TCM 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
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01-4

- The Multi-function Indicator Light (MIL) lights up
after 2 driving cycles (Dcy); check DTC memory
( page 01
-43
and compare with DTC table
page 01
-45
).
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 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); check DTC
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pair&id=AUDI.B5.AT02.01.1