volkswagen Workshop Repair Guides

Volkswagen Workshop Service and Repair Manuals

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Checking throttle valve potentiometer > < Checking engine operating mode

Passat (B3)

Motronic fuel injection and ignition system ä 07.95
Motronic injection and ignition system
Checking air mass meter

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

  • ● Electrical consumers switched off (radiator fan must not run during the check)
  • ● Air conditioner switched off

Test sequence

  • ‒ Start engine and run at idling speed.
  • ‒ Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit (address word 01); carry out selection at idling.
 
→ Indicated on display:
Rapid data transfer     HELP
Select function XX
  • ‒ Input 08 for "Read measured value block" function and confirm with Q.
 
→ Indicated on display:
Read measured value block     HELP
Input display group number XX
  • ‒ Input 01 for "Display group number" and confirm with Q.
 
→ Indicated on display:
(1...4 = Display zones)
Read measured value block     1     ⇒
     1     2     3     4

Note:

If something different is indicated on the display:

=> Fault reader operating instructions

Only continue with the test when

  • ● The coolant temperature is above 80 °C
    -Display zone 2-
  • ‒ Press C key.
  • ‒ Input 03 for display group 03 and confirm with Q.
 
→ Indicated on display:
(1...4 = Display zones)
Read measured value block 3     ⇒
     1     2     3     4
  • ‒ Check engine load signal in display zone 2:
         Specification: 0...5 %

If the specification is not attained or the figure remains constant when revving-up:

  • ‒ Continue check according to following table.

Display

Cause

Continuation of check

0 %

Open circuit in wire 4

Check wiring => Page 24-42

Short to earth in wire 4

Open circuit in wire 3

Check voltage supply =>24-42

4 %

Short to positive in wire 4

Check wiring

37...38 %

Open circuit in wire 1

Check voltage supply

Checking voltage supply
 
N24-0199
  • ‒ → Separate 4 pin connector to air mass meter.
  • ‒ Connect multimeter to measure voltage at contacts 1+3 of connector.
  • ‒ Switch on ignition.
         Specification: Min. 9 V
  • ‒ Switch off ignition
  • ‒ Reconnect connector.

If no voltage is present:

  • ‒ Check wiring according to current flow diagram.

Checking wiring
 
N24-0178
  • ‒ → Connect test box V.A.G 1598/18 to control unit wiring loom.
 
N28-0199
  • ‒ → Check wiring between test box and 4 pin connector for open circuit according to current flow diagram.
         Contact 2+socket 16
         Contact 4+socket 17
         Wire resistance: Max. 1.5 ω
  • ‒ Check wiring at 4 pin connector for short to one another.
         Contact 2+socket 17
         Specification: ∞ω
  • ‒ Check wire at 4 pin connector contacts 2+4 for short to battery positive according to current flow diagram.

If no wiring fault is detected:

  • ‒ Replace air mass meter (G70).

Checking throttle valve potentiometer > < Checking engine operating mode