SEAT Workshop Service and Repair Manuals

Because the injection system operates with an accelerator pedal sender (potentiometer) which may be defective, the engine is governed for reasons of safety when the brakes are operated. To do this the control unit requires signals from 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 is immediately reduced to idling speed.

Special tools, testers, measuring instruments and auxiliary items required

• ◆ Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
• ◆ Test box V.A.G 1598/18
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test sequence

• ‒ Connect the fault reader V.A.G 1551 (V.A.G 1552) and with ignition switched on select engine electronics control unit with the "Address word" 01.
  (Connecting fault reader and selecting engine electronics control unit .)

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

• ‒ Press keys 0, 0 and 6 for "Display group number 6" and confirm entry with Q key.
• ‒ Observe display in display zone 2.

• ‒ Operate brake pedal slowly.

• ‒ Centre display = Brake pedal switch
• ‒ Right-hand display = Brake light switch

Centre display does not change:

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.

• ‒ Switch off ignition.
• ‒ Pull connector off brake pedal switch =>Fitting locations overview, Page 23-4.
• ‒ → Measure resistance between switch contacts.
      Specification:
      Brake pedal not depressed: less than 10 ω
      Brake pedal depressed:∞ω

If the specification is not obtained:

• ‒ Replace brake pedal switch (F47).

If the specification is obtained:

• ‒ Remove dash panel insert:

=> Electrical system; Repair group 90; dash panel insert; removing and installing dash panel insert

• ‒ → Connect test box V.A.G 1598/18 to control unit wiring loom.

• ‒ → Check wiring between test box and connector for open circuit according to current flow diagram.
      Contact 1+ socket 33
      Contact 2+ socket 20
      Wire resistance: max. 1.5 ω
• ‒ Additionally check wires for short to one another, to vehicle earth and to battery positive.
      Specification: ∞ω

Right-hand display does not change:

• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
• ‒ Switch off ignition.
• ‒ Set multimeter scale to measure voltage and connect between test box sockets 44 + 1.
• ‒ Observe voltage display.
      Specification:
      Brake pedal not depressed: 0 Volt
      Brake pedal depressed: approx. battery voltage

No voltage is displayed:

• ‒ Check whether brake light functions.

Brake light OK:

• ‒ Check wiring to brake light switch for open/short circuit according to current flow diagram.

Brake light not OK:

• ‒ Replace brake light switch (F).