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Testing signals from/to air conditioning system > < Testing auxiliary signals

A4 Mk1

Motronic fuel injection and ignition system (4-cyl.turbo) > 07.96
Testing auxiliary signals
Testing signals from/to automatic gearbox

A - Gear change signal

This signal causes the ignition timing to be briefly retarded (torque reduction) during gearshifts in order to smooth out the jolts experienced when changing gear.

  • ‒ Read measured value block, Display Group 19, engine at idling speed
 
→ Indicated on display:
Read measured value block 19    ⇒
        860 rpm    2.20 ms        1 1    1        8.5 5before TDC
  • ‒ Observe readout in display zone 3.
  • Specified result: X 1 X
Caution
The V.A.G 1551 must be operated by a second person.
  • ‒ Take the vehicle for a test drive.
 
→ Observe display zone 3 during a gear change.
Read measured value block 19    ⇒
        860 rpm    2.20 ms        1 0    1        4.5 5before TDC
  • Specified result: X 0 X

If specified result is not attained:

  • ‒ Connect the V.A.G 1598/22 test box to the wiring harness for the engine control unit.
    .

The following wiring connections should be checked for open circuits and/or short to positive or negative:

Test box V.A.G 1598/22, socket.

Automatic gearbox control unit, contact

23

=> Circuit diagrams, Electrical Fault Finding and Installation Location binder
  • ‒ Rectify short circuit or open circuit if necessary.

B - Accelerator position signal

This signal is required for load-dependent calculation of the gearshift times.

The signal is monitored by the self-diagnosis function (fault memory, read measured value block) of the automatic gearbox control unit.

Checking signal

=> Automatic gearbox; Repair Group 01

C - engine speed signal

This signal is required for calculating how to smooth out the gearshifts.

Checking signal
=> Checking engine speed signal, Page 24-84

D - Selector lever position signal

This signal is required for idling speed stabilization.

When a gear is selected, the idling speed is reduced in order to alleviate vehicle "creeping".

  • ‒ Read measured value block, Display Group 20, engine at idling speed
 
→ Indicated on display:
Read measured value block 19    ⇒
    860 rpm    Neutral    A/C-Low     Compr. OFF
  • ‒ Observe readout in display zone 2.
  • Specified result: Neutral
  • ‒ Operate the foot brake and engage a gear.
 
→ Specified result: Gear selected.
Read measured value block 19    ⇒
    860 rpm     Gear selected     A/C-Low     Compr. OFF

If specified result is not attained:

  • ‒ Connect the V.A.G 1598/22 test box to the wiring harness for the engine control unit.
    .

The following wiring connections should be checked for open circuits and/or short to positive or negative:

Test box V.A.G 1598/22, socket.

Automatic gearbox control unit, contact

22

=> Circuit diagrams, Electrical Fault Finding and Installation Location binder
  • ‒ Rectify short circuit or open circuit if necessary.

E - Signal for changing up or down

In conjunction with the signal for gear change, this signal tells the engine control unit whether the gearbox has changed up or down. This influences the ignition timing retardation.

The signal is monitored by the self-diagnosis function (fault memory, read measured value block) of the automatic gearbox control unit.

Checking signal

=> Automatic gearbox; Repair Group 01

Testing signals from/to air conditioning system > < Testing auxiliary signals