volkswagen Workshop Repair Guides

Volkswagen Workshop Service and Repair Manuals

Checking air mass meter > < Checking components
Motronic injection and ignition system (6-Cyl. engine)
Checking components
Checking Lambda probe heating

Special tools, testers, measuring instruments and auxiliary items required

  • ◆ 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

Check conditions

  • ● Fuse 18 must be OK.
  • ● The battery voltage must be at least 11.5 V.
  • ● Fuel pump relay must be OK

Test sequence

 
N24-0279
  • ‒ → Separate 4 pin connector (black) to Lambda probe before catalyst (G39) -1-.
 
N24-0607
  • ‒ → Check probe heating at connector contacts 1+2 for continuity

If the specification is not attained:

  • ‒ Replace Lambda probe (G39).

If the specification is attained:

 
N24-0220
  • ‒ → Connect multimeter to measure voltage at contacts 1+2 of connector to Motronic control unit.
  • ‒ Start engine and run at idling speed.
  •      Specification: 11...15 V
  • ‒ Switch off ignition.

If no voltage was present:

 
V29-0062
  • ‒ → Connect test box V.A.G 1598/18 to control unit wiring loom.

Vehicles08.95 ▸

 
N24-0220
  • ‒ → Check wiring between test box and 4 pin connector for open circuit according to current flow diagram.
         Contact 2+socket 12
         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.

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

If no wiring fault is detected:

  • ‒ Replace Lambda probe (G39).

Vehicles ▸07.95

 
N24-0220
  • ‒ Pull relay for Lambda probe heating (J278) out from relay chamber.

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

  • ‒ → Check wiring between 4 pin connector contact 1 + chamber 8 on relay connector for open circuit according to current flow diagram:
         Specification: max.1.5 ω
  • ‒ Additional check wiring between connector contact 2 + engine earth for open circuit:
         Specification: max.1.5ω
  • ‒ Check wiring for short circuit to one another
         Contact 1 + 2
         Specification: ∞ω
  • ‒ Switch on ignition.
  • ‒ Bridge test box sockets 1+9.
  • ‒ Measure activation voltage at relay chamber pin 6:
  •      Specification: At least 11.5 V

No voltage is displayed:

  • ‒ Check wiring to current supply relay (J271) according to current flow diagram.

If no wiring fault is detected:

  • ‒ Renew current supply relay (J271).
  • ‒ Then bridge test box sockets 1+6.
  • ‒ Measure activation voltage of relay connector 2:
  •      Specification: At least 11.5 V
  • ‒ Switch off ignition.

If no voltage was present:

  • ‒ Check wire from fuse 18 to relay chamber pin 2 for open circuit.

If not open circuit can be found:

  • ‒ Check wire between test box socket 28 and relay chamber pin 4 for open circuit using current flow diagram.
         Specification: Max. 1.5 ω

If the specifications are attained:

  • ‒ Renew Lambda probe heating relay (J278).

Checking air mass meter > < Checking components