Transmission Control Systems: Service and Repair

EFFECT OF DISCONNECTION OR TOTAL DISCHARGE OF THE BATTERY ON ELECTRICAL SYSTEMS IN THE VEHICLE, SUBSEQUENT MEASURES

NOTE:
- In order to avoid triggering the alarm siren (installed on right next to the battery) of vehicles with M 536, the battery must be disconnected with the ignition on.
- All loads must be switched off beforehand.
- Never disconnect battery with engine running.
- Never start engine without securely connected battery.
- Do not use a boost charger to start the engine.
- Whenever possible, use jump leads with overvoltage protection.
- Always disconnect both battery terminals before carrying out welding work on the vehicle.
- Wiring harness plugs of control modules or other electronic components must be connected or disconnected with the ignition off. Exception: vehicles with the additional equipment M 536 (alarm siren with tilt sensor).

CONTROL MODULE MEMORIES

Problem
Values and faults stored in the control modules can be deleted if the battery is disconnected or completely discharged.

Remedy
If possible, all fault memories should be checked and, if necessary, printed out before the battery is disconnected.

SUPPLY VOLTAGE FAULT ENTRY

Problem
The entry supply voltage could be stored in various control modules if the battery has been completely discharged.

Remedy
Delete the "supply voltage" entry from the control modules in question.

TEST DRIVE AFTER CONNECTING THE BATTERY

NOTE: The fault memories of all vehicle control modules should be read out again after the test drive.

DME CONTROL MODULE

NOTE: With all DME systems, the engine must run for several minutes before the engine control module can relearn the idle speed and mixture adaptation values.

Problem
- After disconnection of the power supply, the idle speed might change or fluctuate briefly until the idle speed positioner (M 5.2) or the throttle adjusting unit (ME 7.2) is readapted.
- The mixture adaptation is also lost.

Remedy
After the battery is connected.

With the DME ME 7.2, it is necessary to carry out a learning and adaptation routine as described below:

1. Switch the ignition on for 1 minute without starting the engine. Do not actuate accelerator pedal.
2. Switch off ignition for at least 10 seconds.

This completes the adaptation of the throttle adjusting unit.

TIPTRONIC

Problem
The stored pressure adaptation values are lost if the power supply to terminal 30 is interrupted. This can result in poor shifting quality and rough shift operations during the adaptation phase.

Remedy
- Carry out a test drive and drive the vehicle with different loads and at different speeds so that all shift functions (manual and automatic programme) are executed at least once.

This readapts the shifting pressures of the system and thereby re-establishes smooth shifting.

POWER WINDOWS

Problem
The limit positions of the power windows are deleted from the control module when the battery is disconnected and connected.

Remedy
- Manually close each power window as far as it will go, then press the rocker switch for closing the window again.

The limit position of the respective power window is now stored in the control module again.

INSTRUMENT CLUSTER

The trip counter is set to 0 when the power supply is disconnected.

CLOCK

NOTE: In the case of vehicles with PCM, the date and time are deleted when the battery is disconnected.

Problem
Depending on the software version, the clock is set to 12:00 a.m. or 1:00 a.m. when the power supply is disconnected.

Remedy
- Enter the current time again.

FUEL LEVEL DISPLAY

Problem
- If the power supply is interrupted by a discharged or disconnected battery with the tank containing less than 19 I, the calculated value for the range on remaining fuel in the instrument cluster will be incorrect or deleted.
- If the tank contains less than 10 I, it is possible that the fuel level warning light is no longer activated.
- If the power supply is restored with the fuel level at less than 19 I, it is possible that the fuel level display may subsequently display too much.

This may lead to the vehicle breaking down.

Remedy
- Refill at least 19 I of fuel; then the fuel level sensor is in operating range and its display precision is guaranteed.

RADIO

Problem
The radio reverts to the Code function when the battery is disconnected and is thus no longer ready for operation.

Remedy
1. Input the radio code.
2. If the code card is unavailable, the radio code can also be read from the DME control module (under "Vehicle data").
3. This code is also available from the Porsche IPAS.

PCM

Problem
- The PCM reverts to the Code input function when the battery is disconnected and is thus no longer ready for operation.
- When the power supply is disconnected, the built-in GPS receiver loses the so-called almanac containing the satellite orbital paths.
- The date and time are deleted when the battery is disconnected.
- Radio stations stored by the customer are no longer displayed.
- If the telephone card was inserted and the telephone was ready for operation, the telephone is subsequently disabled.

Remedy
1. Input the PCM code. If the code card is unavailable, the PCM code can also be read from the DME control module (under "Vehicle data").
2. This code is also available from the Porsche IPAS.
3. Switch on the PCM with a free panoramic view for approx. 20 minutes (to load GPS almanac).
4. The date and time are also adopted once the GPS almanac has been loaded; it may be necessary to change over to summer time (daylight-saving time).

This time is transferred to the instrument cluster. If the time is then manually changed by means of the instrument cluster, this time is adopted by the PCM and synchronized with GPS time.

1. The stored stations are displayed again when station buttons 1 to 6 are pressed.
2. The telephone is enabled again when the telephone PIN code is entered with the SIM telephone card inserted.