Volkswagen Workshop Service and Repair Manuals

Note:

Only gold-plated contacts may be used when servicing the sender connector contacts

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 1551/3A
• ◆ 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

Test sequence

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

• ‒ Read off the displayed value for intake manifold pressure in display zone 2 and note this value.
• ‒ Briefly open throttle valve. The intake manifold pressure value must increase briefly.

If the display shows constantly 91 mbar or 1254 mbar:

Continuation of check when display shows 91 mbar:

• ‒ → Pull 4 pin connector off intake manifold pressure sender (G71) with intake air temperature sender (G42) -arrow- (engine can stall).

• ‒ → Bridge connector contacts 3+4 with aux. cables from V.A.G 1594 and observe display.

If the display jumps to 1254 mbar:

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

• ‒ Renew the intake manifold pressure sender (G71) with intake air temperature sender (G42)
  => Page 24-20 , item 11 .

If the display remains at 91 mbar:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ → 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 connector using current flow diagram.
       Contact 3+socket 98
       Contact 4+socket 109
       Wire resistance: Max. 1.5 ω
• ‒ Additionally check wiring contact 4 for short to earth and to contact 1.
       Specification: ∞ω

If no fault is detected in the wiring:

• ‒ Renew engine control unit => Page 24-117 .

Continuation of check when display shows 1254 mbar:

• ‒ → Pull 4 pin connector off intake manifold pressure sender (G71) with intake air temperature sender (G42) -arrow- (engine can stall).

If the display jumps to 91 mbar:

• ‒ Press ⇒key.
• ‒ Press keys 0 and 6 for the function "End output" and confirm entry with the Q key.
• ‒ Switch off ignition.
• ‒ Renew the intake manifold pressure sender (G71) with intake air temperature sender (G42)
  => Page 24-20 , item 11 .

If the display remains at 1254:

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

• ‒ Release connector from control unit and pull off.

• ‒ → Check wiring to control unit connector at 4 pin connector contact 4 for short to wire contact 3 and to battery positive.
       Specification: ∞ω

If no fault is detected in the wiring:

• ‒ Renew engine control unit => Page 24-117 .