Input signals
The control unit processes signals from various nodes; information comes from:
Automatic transmission selector lever with multifunction switch. The position of the lever controls the switching on of the reversing headlights, the starter lock when the driving mode is on, and the control of the driving mode change system.
Buttons «Sport», which includes a sports switching program (not in gearbox with DSP).
Throttle potentiometer for throttle position. This element, familiar from the injection system, is used to determine the switching points.
Speed sensor in the automatic transmission to determine the driving speed, also for shift points. In the event of a malfunction of this sensor, the control unit uses the engine speed (signal from the ignition system) as a backup indicator.
Accelerator Pedal Limit Sensor (in cable drive «gas», the 6-cylinder engine is located separately); it reports if the accelerator pedal has been fully depressed. In this case, the upshift occurs later, if necessary, the automatic transmission switches down two ranges.
Brake light switch to unlock the shift lever. Lever out of position «R» or «N» in one of the ranges of movement can only be moved when the brake pedal is depressed.
An ATF temperature sensor that reports the temperature of the fluid in the automatic transmission. Significant heating of the ATF can occur due to a large difference in the speed between the engine and the automatic transmission. If the control unit receives a signal «fever», then the automatic transmission in some ranges later shifts to a higher gear. This reduces slippage in the torque converter and lowers the temperature of the ATF - then it switches back to the normal driving program.
Switchover management
If you move the selector lever to the «D», the pressurized ATF reaches the shift valves in the valve block, which in turn hydraulically control the multi-disc clutches and multi-disc brakes. The control unit regulates the pressure by means of solenoid valves and thus determines the time for upshifting or downshifting, as well as shift transitions. Commands from the control unit go further to the shift lever lock magnet, the starter and reverse headlight lock relay and the indicator light in the button «Sport». If the vehicle is equipped with a speed control system, then power does not start to be supplied from the control unit only when one of the forward ranges is turned on and the speed has crossed the 30 km / h limit for the first time.
Self-diagnosis
The automatic transmission control unit can recognize and record faults that occur. The control program monitors the input and output signals of almost all sensors and nodes, as well as their electrical circuits. If you suspect a malfunction in the automatic transmission control, you can only interrogate the memory of the fault memory in an Audi workshop.
Operation in emergency conditions
If the control unit has detected a malfunction that significantly affects the operation, or if the control unit itself is faulty, then it switches to the mode «emergency operation». There are two programs for this:
As before the fault was detected, the automatic transmission shifts up or down automatically, but shifting jerks become much more pronounced.
The automatic transmission no longer automatically upshifts or downshifts. In selector lever positions «D», «3» And «2» only the third range remains available. Only in positions «1» And «R» the selected range is indeed included.
This diagram makes the connections between the shift valve block clearer (1) automatic transmission, selector lever (2), multi-function switch (3) and electronic control unit (4). Manual valve (5) driven directly by the shift lever. Depending on the year of manufacture and engine version, the control unit is equipped with 2 programs for sports and normal driving or is it an automatic transmission with DSP (dynamic switching program), which, depending on the driving style, includes one of 5 programs.
In both cases, an urgent visit to an Audi workshop is necessary, where the memory of the fault memory will be interrogated first.
Automatic transmission with DSP
From 7/92 Audi-100 with 6-cylinder engines are equipped with front and quattro drive and a four-speed automatic transmission with the so-called dynamic shift program «DSP». The electronic control unit of this gearbox has five modes with its own symbol. The advantage of an automatic transmission with DSP is its «ability to improve»: The control unit continuously sums the frequency of different running conditions and automatically selects the mode corresponding to the current style with a directly marked symbol. Earlier and correspondingly later shifting to a higher or lower stage of the DSP gearbox «automatically» turns on with its five modes, as said, «sports», and especially «economical» driving way.
Automatic transmission check
The AKP provides almost no opportunities for self-initiative testing at home. Targeted checks, however, help to assess the cause of the malfunction, which is not the least interesting when buying a used car:
In case of malfunctions, first of all, it is necessary to check the ATF level in the automatic transmission.
If the ATF smells burnt at the tip of the dipstick, then there is serious damage to the automatic transmission. In this case, the multi-plate clutches or brake bands are defective.
During a test drive, you can check the switching points.
From how the switching processes take place, one can draw a conclusion about the state of the automatic transmission. О Adjustment of the throttle cable with an integrated accelerator pedal position sensor is an important prerequisite for perfect operation.
The same can be said about the adjustment of the selector lever cable drive.
Monitoring of switching processes
During the test drive, you should pay attention to the switching processes:
Upshifting: when the accelerator pedal is not fully depressed, the shifting is almost imperceptible; when the accelerator pedal is fully depressed or when it is pressed sharply, the gear changes become more noticeable, but the upshift should turn on smoothly. A short-term increase in speed when changing gears indicates problems that should be dealt with more closely.
Downshifting: with the accelerator pedal released (when coasting) and very low speeds is almost imperceptible. It is quite normal to jerk when downshifting on an incomplete or full «gas». Switching to a lower gear with the selector lever with the accelerator pedal released takes 1-2 seconds. If the accelerator pedal is depressed at the same time when shifting with the selector lever, the gear change must take place without delay.
Hint: Audi-100 with automatic transmission cannot be towed more than 50 km, otherwise there is not enough automatic transmission lubrication. For the same reason, the maximum speed of 50 km/h must not be exceeded when towing. In doubtful cases, it is better to take a shorter route or call a tow truck.
Removing the automatic transmission
Front wheel drive vehicles must be raised and secured. Use a large garage jack to support and lower a very heavy automatic transmission.
Disconnect battery.
Disconnect the wire end to the tachometer sensor.
On models with a 6-cylinder engine, remove the intake duct between the air filter and the intake manifold.
On models with a split ATF filler pipe, loosen it at the top and pull it out. Close the lower part of the pipe with a non-fibrous rag.
Unscrew the bolts connecting the engine and automatic transmission, which can be reached from above. Note for yourself which bolts from which holes you got (for later assembly).
Support the engine securely to prevent it from tipping over.
Unscrew the bottom panel of the engine compartment.
Remove the thermal protection of the drive shaft.
Remove body crossmembers below exhaust pipe or catalytic converters (depending on engine type).
Remove exhaust pipes (for models with a 6-cylinder engine together with catalytic converters).
Disconnect drive shafts from gearbox (don't let them fall).
Remove starter. This opens access to the torque converter mounting bolts.
Loosen a total of three torque converter bolts on the engine side. To do this, hold the central bolt of the pulley or damper (depending on engine type) using a spanner wrench. Rotate the crankshaft ⅓ of a turn accordingly.
Unscrew the thermal protection of the multifunction switch.
Remove the plug on the gearbox housing. After that, remove the procon-ten system holders from the loops and press the cables upwards.
Place a container under the bolted connections of the ATF lines.
Unscrew fasteners for ATF lines and move hoses to one side.
Unscrew the front engine bracket, if equipped.
Raise the automatic transmission with a garage jack and loosen the automatic transmission mounting bolts.
Tilt the engine connected to the automatic transmission slightly back; after that, again bring a solid support under the engine.
Unscrew the gearbox support on the right side of the gearbox.
Unhook the retaining clips of the automatic transmission control lever rod and remove the control lever cable.
Unscrew the lower connecting bolts securing the automatic transmission to the engine.
Move cardan shafts back.
Press the automatic transmission from the engine; if necessary, use the mount.
Carefully lower the automatic transmission.
When removing the automatic transmission, press the torque converter from the driven disk.
The torque converter must remain together with the automatic transmission! Be careful not to fall out (screw with wire).
Installing an automatic transmission
Installation takes place in the reverse order compared to removal. The following points deserve special attention:
Check whether the torque converter is installed correctly in the automatic transmission. Make sure that it does not move forward during installation.
To screw the torque converter to the flywheel, be sure to use the original bolts, otherwise the torque converter will be destroyed.
Top up with new ATF if necessary.
Install exhaust pipe.
Adjust the selector lever.
Tightening torques for automatic transmission fasteners
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