Audi A4

since 1994 release

Repair and operation of the car

Entrance signals

Information comes to the electronic control unit from:

• the lever selector with the multipurpose switch of situation. Installation of the lever inclusion of lamps of a backing, the blocking mechanism of a starter at the included range of change of transfers copes, and also inclusion/switching off of the device of adjustment of speed;
• potentiometer of a butterfly valve about its situation. It is the knot known on injection, serves for calculation of points of gear shifting;
• the speed sensor in a transmission for determination of speed of the movement, and also gear shifting points. If this sensor is faulty, the signal from the Hall sensor undertakes;
• the sensor about number of turns on a transmission entrance. Also settles down on a transmission and serves for definition of points of gear shifting;
• the accelerator sensor in a cable of a butterfly valve; it gives a signal when the pedal of gas is wrung completely out. After that there is a switching on higher transfer or if it is necessary, there is a switching on one or two ranges of change of transfer number down;
• the switch of brake fires for unblocking of electromagnetic blocking of the lever selector. The lever selector moves from situation "P" or "N" in one of ranges of change of transfer number only at the pressed brake pedal;
• ATF temperature sensor in a transmission. When the signal "the increased temperature" comes to the control unit of the engine, in the separate ranges of change of transfer number there is a switching on higher level. It reduces a gap in the hydrotransformer and reduces ATF temperature – only after it there is a switching on the standard program.

Management of gear shifting process

If you move the lever selector to the situation "D", ATF, being under pressure, comes to the so-called switching gates in a box which in turn operate in the hydraulic way lamellar couplings and brakes. The control unit regulates pressure by means of electromagnetic valves and, in such a way, defines the switching moment on higher or low transfer, and also switching transitions. At the same time there is a communication with the control unit of ignition/injection – when switching on higher transfer the moment of ignition is slightly removed in order that switching proceeded softly.

Signals from the control unit arrive further to the electromagnet of blocking of the lever selector combined by the relay of blocking of a starter and to backing lamps. If Audi A4 is supplied with system of adjustment of speed, the control unit of automatic equipment of a transmission gives on it tension only when the range of change of transfer number of forward transfer is included and the speed of 30 km/h is for the first time exceeded.

Self-diagnostics

The control unit of an electronic transmission can distinguish the arising defects and keep them in the computer. The arising failures are remembered in a long-term memory. The memory can be interrogated in a workshop. It becomes by means of the reading-out device; unfortunately, opportunity for poll of the computer by the fan is not provided. If you assume existence of malfunction in management of a transmission, you will be able to consider memory of the computer only in Audi workshop.

Emergency course

4-staged AKP

If the control unit distinguished defect which has essential negative impact on functioning, or the control unit is faulty, the mode of "the emergency course" joins. For this purpose there are two emergency programs:

• If the lever selector is in the situation "D", "3" or "2", the transmission includes in the hydraulic way the 3rd transfer. The chosen range of change of transfer number joins only in provisions of the 1 and R lever selector.
• If the signal of number of turns of the engine and speed does not arrive and pressing of a pedal of an accelerator for the first time exceeds value ѕ, the transmission switches to a step of "N", i.e. there is no more drive. By switching off of ignition and new start of the engine you can try to make active a transmission again.

Emergency course

Transmission 5-HP-18

The transmission has different modes of the emergency course depending on nature of malfunction:

• At insignificant failure the movement is carried out on other program of gear shifting.
• At defect in mechanical part of knot of gear shifting during the movement the transmission remains included at the 4th step. Then after switching off of the engine the 3rd range of change of transfer number joins just.

Check of an automatic transmission

The automatic transmission practically does not leave to the fan of opportunities for his initiative. But purposeful check will help to localize malfunction that not least is of interest upon purchase of the second-hand car:

• With malfunction first of all check the ATF level in a transmission.
• If ATF on the probe for its measurement smells burned, there is a heavy damage of a transmission. In this case brake tapes or plates of coupling can be defective.
• At a trial trip you can check gear shifting points.
• How there is a gear shifting process, gives information on a condition of a transmission.
• Adjustment of a cable of a butterfly valve with the integrated switching mechanism by sharp pressing of a pedal of gas is an important condition of a faultless operating mode.
• The same belongs to adjustment of a cable of the lever selector.

Gear shifting process assessment

During a trial trip you can pay the attention to gear shifting process:

Switching on higher transfer: at partially wrung out gas pedal transfer change is almost not felt; at full gas or sharp pressing a gas pedal transitions become more distinct, but higher transfer has to grab always softly. Short increase of frequency of rotation of the engine at change of transfer indicates defect which has to be studied more attentively.

Switching on lower transfer: without gas (when swing) it is hardly notable at very low speeds. The push when switching on a backing on partial or full gas is normal. The return switching without gas the lever selector lasts one-two seconds. If at compulsory switching back the lever selector gas at the same time increases, gear shifting happens without delay.