Volkswagen Workshop Service and Repair Manuals

Special tools, testers and auxiliary items

• ◆ 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 conditions

• ● Fuel pump relay OK

• ● Fuse 18 OK

Test sequence

• ‒ → Separate 4 pin connector (black) to Lambda probe before catalyst (G39) -1-.

• ‒ → Check probe heating at connector contacts 1+2 for continuity
       Specification: max. 200 ω

If the specification is not attained:

• ‒ Replace Lambda probe (G39).

If the specification is attained:

• ‒ → Connect multimeter to measure voltage at contacts 1+2 of connector.
• ‒ Switch on ignition.
       Specification: approx. 4.5 V
• ‒ Start engine and run at idling speed.
       Specification: 0... 11 V fluctuating
  (Heating is pulsed)
• ‒ Switch off ignition.

If no voltage is present:

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

• ‒ → Check wiring between test box and 4 pin connector for open circuit according to current flow diagram.
       Contact 2+socket 20
       Wire resistance: Max. 1.5 ω

If the specification is attained:

• ‒ Check wiring from contact 1 to fuel pump relay (J17) according to current flow diagram.