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 1598/22
• ◆ 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 must be at least 80 °C, =>display group 04, display zone 3.
• ● Exhaust system between catalyst and cylinder head must be free of leaks

Functional check

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552). Start engine and select "Address word" 01 of engine control unit. When doing this the engine must be running at idling speed.
  (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, 3 and 0 for the "Display group number 30" and confirm entry with Q key.

• ‒ Check Lambda regulation status before catalyst (display zone 1):
       Specification: 1 1 1
  

If the specification is not obtained:

• ‒ Check the Lambda probe heating before catalyst
  => Page 24-26 .

Significance of 3 digit number block in display zone 1:

If the specification is obtained:

• ‒ Change to display group 32 as follows:
• ‒ Press C key.
• ‒ Press keys 0, 3 and 2 for "Display group number 32" and confirm entry with Q key.

• ‒ Check Lambda learnt values at idling speed (additive) in display zone 1.
       Specification: -10.0...10.0 %
• ‒ Check Lambda learnt values at part load (multiplicative) in display zone 2.
       Specification: -10.0...10.0 %

If the specification is not obtained:

• ‒  , Evaluating display group 32

If the specification is obtained:

• ‒ Change to display group 33 as follows:
       V.A.G 1551: Press key 3
       V.A.G 1552: Press key ↑

• ‒ Observe Lambda regulation in display zone 1. The display must fluctuate at least 2 % in the range
       -10.0...10.0 %
• ‒ Check Lambda probe voltage in display zone 2. The voltage must
       fluctuate at least 20 times per minute
  in range of
       0... 1.0 V.

If the display in display zone 2 remains constantly at a value:

• ‒ Continue check according to following table.

If the Lambda regulation in display zone 1 does not fluctuate as stated:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
• ‒ Carry out road test and burn Lambda probes clean and repeat check.

Observe the valid safety precautions when carrying out a road test => Page 24-22 .

If the the specifications in display zone 1 are not obtained even after a test drive, or the value does not fluctuate by at least 2 %:

• ‒ Check Lambda probe before catalyst for ageing

Checking basic voltage

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

• ‒ → Connect multimeter with aux. cables from V.A.G 1594 to measure voltage at contacts 3+4 (connector to engine control unit).
• ‒ Switch on ignition and measure basic voltage.
       Specification: 0.40...0.50 V
• ‒ Switch off ignition.

If the specification is not obtained:

• ‒ Check Lambda probe wiring
  => Page 24-99

If the specification is obtained:

• ‒ Replace the Lambda probe before catalyst (G39).

Checking Lambda probe wiring

• ‒ → Connect test box V.A.G 1598/22 to control unit wiring harness.

• ‒ → Check wiring between test box and 4 pin connector (to control unit) for open circuit according to current flow diagram.
       Contact 3+socket 25
       Contact 4+socket 26
       Wire resistance: Max. 1.5 ω
• ‒ Check wiring at connector contacts 3+4 for short circuit to contacts 1+2 using current flow diagram.
       Specification: ∞ω

If no fault is detected in the wiring:

• ‒ Replace the Lambda probe before catalyst (G39).