Volkswagen Workshop Service and Repair Manuals

Special tools, testers and auxiliary items

• ◆ 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

Check conditions

• ● Coolant temperature at least 80 °C
• ● Exhaust system between catalyst and cylinder head free of leaks

Functional check

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit (address word 01); carry out selection at idling.
  

• ‒ Input 08 for "Read measured value block" function and confirm with Q.

Note:

If something different is indicated on the display:

=> Fault reader operating instructions

• ‒ Input 01 for "Display group number" and confirm with Q.

• ‒ Read Lambda factor in display zone 3.
       Specification: Display fluctuates around 1

If the probe factor does not fluctuate as stated:

• ‒ Carry out road test and burn Lambda probe clean and repeat check.

If the specifications are not obtained again:

• ‒ Check Lambda probe heating => Page 24-35 .

If the displayed figure remains constant:

• ‒ Press ⇒ key.
• ‒ Input 06 for "End output" and confirm with Q.
• ‒ Switch off ignition
• ‒ Continue check according to following table.

Checking basic voltage

• ‒ → Separate 4 pin connector to Lambda probe.
• ‒ Start engine and run at idling speed.
• ‒ Connect multimeter to measure voltage at contacts 3+4 of connector.
       Specification: Approx. 0.45 V
• ‒ Switch off ignition

If the specification is not obtained:

• ‒ Check Lambda probe wiring => Page 24-33

Checking Lambda probe wiring

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

• ‒ → Separate 4 pin connector to Lambda probe.
• ‒ Check wiring between test box and 4 pin connector for open circuit according to current flow diagram.
       Contact 3+socket 42
       Contact 4+socket 20
       Wire resistance: Max. 1.5 ω

• ‒ → Check wiring at 4 pin connector for short to one another.
       Contact 1+socket 20
       Contact 1+socket 42
       Contact 2+socket 42
       Contact 2+socket 20
       Contact 3+socket 20
       Specification: ∞ω
• ‒ Check screening for short to the probe wiring according to current flow diagram.
       Contact 3+socket 56
       Contact 4+socket 56
       Specification: ∞ω

If the specifications are not attained:

• ‒ Check wiring according to current flow diagram.

If no wiring fault is detected:

• ‒ Renew Lambda probe (G39).