Audi Workshop Service and Repair Manuals

Special tools and workshop equipment required

• ◆ V.A.G 1526 A
• ◆ V.A.G 1527 B
• ◆ V.A.G 1594 A
• ◆ V.A.G 1598/31
• ◆ VAS 5051 with VAS 5051/1

• or

• ◆ V.A.G 1551 with V.A.G 1551/3 A

Because the injection system operates with an accelerator pedal sender (potentiometer) which may be defective, the engine is throttled back for reasons of safety when the brakes are applied To do this the control unit requires signals from the brake light switch and also the brake pedal switch. This means that if the brakes are operated when the accelerator pedal is held at a constant position the engine speed is immediately reduced. Incorrectly adjusted switches may lead to unrequired regulating action.

• ‒ 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 should be switched on.

• ‒ Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

• ‒ Press keys 0, 6 and 6 to select "Display Group 66" and confirm entry with Q key.

• ‒ Observe display in display zone 2.

• ‒ Depress brake pedal

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

• ‒ Allow brake pedal to return slowly to its normal position.
• ‒ Both readouts should return from 1 to 0.

If one or both of the readouts does not change:

• ‒ Test voltage supply
  => Page 24-186.

Testing voltage supply

• ‒ Remove storage compartment on driver's side.

=> General body repairs, Interior; Repair group 68; Dash panel; Removing driver's storage compartment

• ‒ Unplug 4-pin connector on brake pedal.
• ‒ Connect hand-held multimeter (voltage range) between the following sockets on the connector:
• ‒ Switch ignition off.

• ‒ Switch ignition on.

If specifications are met:

• ‒ Test wiring connections => Page 24-186.

If specifications are not met:

• ‒ Test wiring connections from sockets 1 and 3 of connector for open circuit or short to earth.

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

• ‒ Rectify any open/short circuit as necessary.

Checking wiring connections

• ‒ 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 24-26.

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

Resistance in wiring: max. 1.5 Ohm

• ‒ Rectify any open/short circuit as necessary.

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

If no open circuits are found in wiring:

• ‒ Renew brake light switch / brake pedal switch.