Audi Workshop Service and Repair Manuals

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 1551/3
• ◆ 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

Check conditions

• ● The fuses must be OK.
• ● The battery voltage must be at least 11.5 V.
• ● Fuel pump relay must be OK

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, 4 and 1 for "Display group number 41" and confirm entry with Q key.

• ‒ Check status of Lambda probe heating before catalyst in display zone 2:
      Display: Htg.bC.ON

Note:

The Lambda probe heating may be switched on or off depending on the operating mode of the engine, therefore the display in display zone 2 may show "Htg.bC.ON or alternating from Htg.bC.ON to Htg.bC.OFF.

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

If the specification is not obtained:

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

• ‒ → Check probe heating for continuity at Lambda probe connector contacts 1 and 2.

Note:

The heater element resistance is approx. 1...5 ω at room temperature. Even slight increases in room temperature increase the resistance greatly.

If it is determined that probe heating has an open circuit:

• ‒ Renew Lambda probe before catalyst (G39)
  , item 13.

If probe heating has continuity:

Checking voltage supply

• ‒ 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).
• ‒ Start engine and run at idling speed.
      Specification: 11.0...15.0 V

• ‒ Switch off ignition.

If no voltage is present:

• ‒ → Connect test box V.A.G 1598/22 to control unit wiring harness
  => Page 24-121.

• ‒ → Check wires between test box and 4-pin connector (connector to control unit) for open circuit using current flow diagram.
  Contact 2+socket 13
      Wire resistance: max. 1.5 ω

If the specification is obtained:

• ‒ Check wire between 4 pin connector contact 1 and fuel pump relay (J17) for open circuit using current flow diagram.
      Wire resistance: max. 1.5 ω