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
       ▸ 07.93: Cable V.A.G 1551/1
       08.93 ▸: 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 sequence

• ‒ Remove air cleaner or air intake elbow.
• ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit (address word 01); carry out selection with ignition switched on.
  

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

• ‒ Input 00 for "Display group number" and confirm with Q.

• ‒ Slowly open throttle valve fully and observe the numerical figures in display zones 2 and 3.

• Display zone 2:
       The numerical figure must increase uniformly until throttle                valve is 1/4 open and then remain constant
• Display zone 3:
       The numerical figure must increase uniformly over the entire
       range

• ‒ Press ⇒ key.
• ‒ Input 06 for "End output" and confirm with Q.

If one or both figures remain constant:

• ‒ Switch off ignition
• ‒ → Pull 5 pin connector -1- off throttle valve potentiometer -2-.
• ‒ Connect multimeter with aux. cables from V.A.G 1594 to measure voltage at contacts 1+5 of the connector.
• ‒ Switch on ignition and measure voltage
       Specification: approx. 5 V

• ‒ → Connect test box V.A.G 1598/18 to control unit wiring loom.
• ‒ Check wiring between test box and 5 pin connector for open circuit according to current flow diagram.
       Contact 1+socket 17
       Contact 2+socket 41
       Contact 4+socket 18
       Contact 5+socket 14
       Wire resistance: Max. 1.5 ω
• ‒ Additionally check wires for short to one another.
       Specification: ∞ω

If no wiring fault is detected and voltage was present between contacts 1+5:

• ‒ Replace lower part of injection unit.

If no wiring fault is detected and no voltage was present between contacts 1+5:

• ‒ Renew Mono Motronic control unit (J257)
  , item 2 .