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

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
  

Significance of 3 digit number block in display zone 1:

If the specification is not obtained:

• ‒ Check the Lambda probe heating before catalyst
  => Page 24-33 .

If the specification is obtained:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 4 for the function "Initiating basic settings" and confirm entry with Q key.

• ‒ Press keys 0, 3 and 4 for "Display group number 34" and confirm entry with Q key.

• ‒ Rev. up twice to over 5,000 rpm.
• ‒ Set engine speed to 1500...3900 rpm using speed regulator V.A.G 1788/10:
• ‒ Maintain this engine speed until "TEST ON" appears in
       display zone 4.

• ‒ Continue to maintain the same speed until
       specification "B1-P1 OK"
  appears in display zone 4.

If "B1-P1 n.OK"
     appears in display zone 4,

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

• ‒ Press keys 0, 3 and 3 for "Display group number 33" and confirm entry with Q 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 24-29 .

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 %:

• ‒ Replace Lambda probe before catalyst (G39).

Checking basic voltage

• ‒ → Separate the 6-pin connector (black) 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 Lambda probe before catalyst (G39).

Checking Lambda probe wiring

• ‒ → 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 6-pin connector (to control unit) using current flow diagram.
       Contact 3+socket 52
       Contact 4+socket 71
       Contact 5+socket 70
       Contact 6+socket 51
       Wire resistance: Max 1.5 ω
• ‒ Check the wiring at connector contacts 3+4 for short circuit to contacts 1+2.

If no fault is detected in the wiring:

• ‒ Replace Lambda probe before catalyst (G39).