Volkswagen Workshop Service and Repair Manuals

Special tools, workshop equipment, 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 1598/31
• ◆ 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). Then switch ignition on and select engine control unit with the "Address word" 01.
  (Connecting fault reader and selecting engine control unit .)

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

• ‒ Press keys 0, 6 and 6 for "display group 66" and confirm with Q key.

• ‒ Observe display in display zone 2:
  (3rd and 4th positions from left)
       Specification: x x 0 0
• ‒ Depress brake pedal fully and observe display in display zone 2.
       Specification: x x 1 1
• ‒ Press the ⇒key.
• ‒ Press keys 0 and 6 for the "End output" function and confirm input with the Q key.
• ‒ Switch off ignition.

If the specification is not obtained:

• ‒ Remove the shelf on driver's side:

=> General body repairs, interior; Repair group 68; Dash panel; Removing driver's side shelf

• ‒ Pull the connector off brake light/brake pedal switch.

• ‒ → Connect the multimeter to measure resistance between contacts 1 and 4.
       Specification: ∞ ω (no continuity)
• ‒ Depress brake pedal.
       Specification: approx. 0 ω
• ‒ Connect the multimeter to measure resistance between contacts 2 and 3.
       Specification: approx. 0 ω
• ‒ Depress the brake pedal.
       Specification: ∞ ω (no continuity)

If the specifications are not attained:

• ‒ Replace the brake light/brake pedal switch.

If the specifications are obtained:

• ‒ → Connect multimeter to measure voltage between contact 1 and earth.
       Specification: at least 11.5 V
• ‒ Switch ignition on.
• ‒ Connect the multimeter to measure voltage between contact 2 and earth.
       Specification: at least 11.5 V

If the specifications are not obtained:

• ‒ Check the wire between 4-pin connector contact 1 and main fuse/contact 2 and central electrics using current flow diagram.

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

If the specification is obtained:

• ‒ → Connect test box V.A.G 1598/31 to control unit wiring harness. The engine control unit remains disconnected.

• ‒ → Check wiring for open circuit between test box and 4-pin connector for open circuit using current flow diagram.
       Contact 3+socket 55
       Contact 4+socket 56
       Wire resistance: Max. 1.5 ω
• ‒ Additionally check wires for short to one another.
• ‒ Additionally check the wiring for short to battery positive or earth.