Volkswagen 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
• ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
• ◆ Adapter set V.A.G 1594
• ◆ Current flow diagram

Check conditions

• ● → Fuse No. 1 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 after catalyst in display zone 4:
       Display: Htg.aC.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 4 may show "Htg.aC.ON or alternating from Htg.aC.ON to Htg.aC.OFF.

If the specification is not obtained:

• ‒ → Separate 4-pin connector to Lambda probe (G130) -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 the Lambda probe after catalyst (G130).

If probe heating has continuity:

• ‒ → 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.
• ‒ Measure the voltage supply:
  When display group 41, display zone 4 displays
  Display, Htg.aC.ON:
       Specification: 11.0...14.5 V
  Display, Htg. aC.ON/Htg.aC.OFF (alternating)
       Specification: Between 0.0...12.0 V fluctuating
• ‒ Switch off ignition.

If no voltage is present:

• ‒ → 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 4-pin connector contact 2 and socket 63
       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