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Audi Workshop Service and Repair Manuals

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Testing auxiliary signals > < Checking brake light switch -F and brake pedal switch -F47

A4 Mk1

Motronic injection and ignition system (4-cyl.)
Testing accelerator position senders -G79 and -G185
Testing clutch pedal switch -F36

This signal prevents engine speed fluctuations and load change jolts when the clutch is disengaged. The signal is also required for the cruise control system.

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

Indicates

Actual speed

Switch positions

Specified speed

Switch positions for cruise control system

Range


off = 0
on = 1


off = 0
on = 1

Specification

0 0 0 0

Note

Relevance of figures
=> Page 24-182

  • ‒ Depress clutch pedal

Relevance of figures in 4-digit readout in display zone 2

x

x

x

x

Display zone 2

X

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

X

Brake pedal switch
0 = Brake pedal not depressed
1 = Brake pedal depressed

X

Clutch pedal switch
0 = Clutch pedal not depressed
1 = Clutch pedal depressed

X

Cruise control system (CCS)
0 = CCS deactivated
1 = CCS enabled

Display zones

1

2

3

4

Display group 66: Signals to engine control unit

Display

xxx /rpm

0 1 0 0

xxx km/h

0 0 0 0

Indicates

Actual engine speed

Switch positions

Switch positions for cruise control system

Range


off = 0
on = 1


off = 0
on = 1

Specification

0 1 0 0

Note

Readout must change from 0 to 1

  • ‒ Allow clutch pedal to return slowly to its normal position.
  • ‒ Readout should return from 1 to 0.

If readout does not change from 0 to 1:

  • ‒ Test voltage supply => Page 24-184.

Testing voltage supply

  • ‒ Remove storage compartment on driver's side.

=> General body repairs, Interior; Repair group 68; Storage compartments, covers and trim parts; Removing and installing driver's storage compartment

  • ‒ Unplug 2-pin connector from clutch pedal.
  • ‒ Switch on ignition.
  • ‒ Connect hand-held multimeter (voltage range) between the following sockets on the connector:

2-pin connector on wiring harness
Socket

Specification

1 + earth

Battery voltage

If specification is obtained:

  • ‒ Test wiring connections => Page 24-185.

If specification is not obtained:

  • ‒ Test for open circuit or short to earth in wiring between fuel pump relay and contact 1 on connector via fuse.

=> Current flow diagrams, Electrical fault finding and fitting locations binder

Testing wiring connection

  • ‒ Connect test box V.A.G 1598/31 to wiring harness for engine control unit. Do not connect to the engine control unit itself.
    => Page 24-10.

Test the following wiring connections for open circuits and short to positive or earth.

2-pin connector on
wiring harness, socket

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

2

39
  • Resistance in wiring: max. 1.5 ω

=> Current flow diagrams, Electrical fault finding and fitting locations binder

  • ‒ Rectify any open/short circuit as necessary.

If no open circuits are found in wiring:

  • ‒ Renew clutch pedal switch.

Testing auxiliary signals > < Checking brake light switch -F and brake pedal switch -F47