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Audi Workshop Service and Repair Manuals

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Checking clutch pedal switch -F36 > < Learning kickdown function

A3 Mk1

Motronic injection and ignition system (4-cyl.)
Checking accelerator pedal position sender -G79 and -G185
Check brake light switch -F and brake pedal switch -F47

As the injection system operates with an accelerator pedal sender (potentiometer), which could be defective, engine-speed regulation is effected for safety reasons when brake is pressed. The control unit requires the brake-light switch and brake-pedal switch signals for this purpose. In other words, if the brake is actuated with the accelerator pedal constantly pressed, the engine speed is immediately regulated to idling speed. Inaccurate switch settings can lead to unintentional speed regulation.

  • ‒ Connect vehicle diagnostic, testing and information system VAS 5051 or fault reader V.A.G 1551 and select engine electronics control unit with "address word" 01 .
    Ignition must be on.
 
→ Indicated on display:
Rapid data transfer    HELP
Select function XX
  • ‒ Press keys 0 and 8 for "Read measured value block" function and confirm entry with Q key.
 
→ Indicated on display:
Read measured value block    
Enter display group number XXX
  • ‒ Press keys 0, 6 and 6 for "Display group number 66" and confirm entry with Q key.
 
→ Indicated on display:
Read measured value block 66    ⇒
    1    2    3    4
  • ‒ Observe readout in display zone 2.

Display zones

1

2

3

4

Display group 66: Signals to engine control unit

Display

xxx km/h

0 0 0 0

xxx km/h

0 0 0 0

Readout

Vehicle speed
(ACTUAL)

Switch positions

Vehicle speed
(SPECIFIED)

Switch positions for cruise control system

Operating range


Off = 0
On = 1


Off = 0
On = 1

Specification

0 0 0 0

Note

Significance of digits
=> Page 24-183

  • ‒ Press brake pedal.

Significance of 4-digit display in zone 2:

x

x

x

x

Display zone 2

X

Brake light switch
0 = Brake pedal not pressed
1 = Brake pedal pressed

X

Brake pedal switch
0 = Brake pedal not pressed
1 = Brake pedal pressed

X

Clutch pedal switch
0 = Clutch pedal not pressed
1 = Clutch pedal pressed

X

Cruise control system (CCS)
0 = CCS disabled
1 = CCS released

Display zones

1

2

3

4

Display group 66: Signals to engine control unit

Display

xxx km/h

0 0 1 1

xxx km/h

0 0 0 0

Readout

Vehicle speed
(ACTUAL)

Switch positions

Vehicle speed
(SPECIFIED)

Switch positions for cruise control system

Operating range


Off = 0
On = 1


Off = 0
On = 1

Specification

0 0 1 1

Note

Both displays must switch from 0 to 1

  • ‒ Allow brake pedal to slowly return to rest position.
  • ‒ Both displays must switch back from 1 to 0.

If one or both of the displays does/do not switch from 0 to 1, check power supply => Page 24-186.

Checking power supply
 
A24-0200
  • ‒ → Connect portable multimeter for voltage measurement to the following connector sockets:
  • ‒ Switch off ignition.

4-pin connector at wiring harness, socket

Specification

1 + earth

Battery voltage
  • ‒ Switch on ignition.

4-pin connector at wiring harness, socket

Specification

2 + earth

Battery voltage

If readings match specifications:

  • ‒ Check wiring => Page 24-186.

If readings do not match specifications:

  • ‒ Check for open circuit/short to earth in wiring from sockets 1 and 2 of connector.

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

  • ‒ If necessary, eliminate open circuit in wiring/short circuit.

Checking wiring

  • ‒ Connect test box V.A.G 1598/31 to engine control unit wiring harness. Actual engine control unit is not to be connected.
 
A24-0200

Check for short to positive/earth and open circuit in the following wiring.

4-pin connector at wiring harness, socket

Test box V.A.G 1598/31, socket

4

56

3

55
  • Resistance: max. 1.5 ohms

=> Current Flow Diagrams, Electrical Fault-finding and Fitting Locations binder

  • ‒ If necessary, eliminate open circuit in wiring/short circuit.

If no open circuit is found in wiring:

  • ‒ Replace brake light switch/brake pedal switch.

Checking clutch pedal switch -F36 > < Learning kickdown function