Audi Workshop Service and Repair Manuals

The engine speed sender (G28) is a speed and reference mark sender. The engine will not start if there is no speed signal. If the speed signal fails when the engine is running, it will cause the engine to stall immediately.

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required

• ◆ Test box V.A.G 1598/22
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Test conditions

• ● The battery voltage must be at least 11.5 V.

Test sequence

• ‒ → Detach black 3-pin connector to engine speed sender -arrow- (on thermostat housing).

• ‒ → Connect multimeter to measure voltage using aux. cables from V.A.G 1594 to contacts 1 (positive) and 3 (earth) on engine speed sender connector.
• ‒ Switch on ignition.
      Specification: min. 4.5 V
• ‒ Switch off ignition.

If no voltage is present:

• ‒ → Connect test box V.A.G 1598/22 to control unit wiring harness
  .

• ‒ → Check wires between test box and 3-pin connector (connector to control unit) for open circuit using current flow diagram.
      Contact 1+socket 62
      Contact 2+socket 53
      Contact 3+socket 67
      Wire resistance: max. 1.5 ω

• ‒ Additionally check wires for short to one another, to vehicle earth and to battery positive.
      Specification: ∞ω

If no wiring fault is detected and voltage was present between contacts 1+3:

• ‒ Replace engine speed sender (G28)
  , item 20.

If no wiring fault is detected and no voltage was present between contacts 1+3:

• ‒ Replace engine control unit
  => Page 24-134.