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

Test conditions

• ● Fuse 18 OK.

Test sequence

• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit with the "Address word" 01. When doing this the engine must be running at idling speed.
  (Connecting fault reader and selecting engine electronics control unit .)

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

• ‒ Press keys 1, 2 and 0 for "Display group number 120" and confirm entry with Q key.

• ‒ Check the resistance value for Lambda probe heating before catalyst (display zone 3):

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.
• ‒ Switch off ignition.

Relevance of figures in 8 digit number block

Continuation

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

• ‒ → Connect multimeter with aux. cables from V.A.G 1594 to measure resistance at contacts 1+2 on connector to Lambda probe.
• ‒ Check the resistance value.
       Specification: 0.0...24.2 ω

If the specification is not attained:

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

If the specification is attained:

• ‒ Set multimeter to "Voltage measurement" range.

• ‒ → Connect multimeter using aux. cables from V.A.G 1594 to measure voltage at contacts 1+2 (connector to engine control unit).
• ‒ Measure the voltage supply:
  When display group 120, display zone 4, 1st position from left = 1
       Specification: 11.0...14.5 V
  When display group 120, display zone 4, 1st position from left = alternately 0 and 1
       Specification: Between 0.0...12.0 V fluctuating

If no voltage is present:

• ‒ → Connect multimeter with aux. cables from V.A.G 1594 to measure voltage at contact 1 (connector to Motronic control unit) and vehicle earth.
       Specification: 11.0...14.5 V

If again no voltage is present:

• ‒ Check wiring from contact 1 to relay plate according to current flow diagram.

If voltage was present:

• ‒ → Connect multimeter using aux. cables from V.A.G 1594 to contact 2 (connector to Motronic control unit) and battery +.
  When display group 120, display zone 4, 1st position from left = 1
       Specification: 11.0...14.5 V
  When display group 120, display zone 4, 1st position from left = alternately 0 or 1
       Specification: Between 0.0...12.0 V fluctuating
• ‒ Switch off ignition.

If no voltage is present:

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

• ‒ → 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 no wiring fault is detected:

• ‒ Replace Motronic control unit (J220).
• ‒ Read-out the readiness code=> Page 01-34 .