Heated Oxygen Sensor (HO2S) -G39- Before Converter, Checking

Heated Oxygen Sensor (HO2S) -G39- For Oxygen Sensor Before Three Way Catalytic (TWC) Converter, Checking

Special tools and equipment
- Scan tool VAG 1551 or VAG 1552 with cable VAG 1551/3
- Test box VAG 1598/22
- Hand multimeter VAG 1526 or multimeter VAG 1715
- Adapter set VAG 1594
- Wiring diagram

Check conditions
- The battery voltage must be at least 11.5 V
- Fuel pump relay must be OK

Test sequence
- Connect VAG 1551 Scan Tool ((VAG 1552). Start engine and select "Address word" 01 of engine control module. When doing this the engine must be running at idle speed. (Connecting scan tool and selecting engine control module [1][2][3]Connecting VAG Scan Tool 1551/1552).

Indicated on display

Rapid data transfer HELP
Select function XX

- Press keys 0 and 8 for function "Read Measuring Value Block" and confirm entry with Q key.

Indicated on display

Read Measuring Value Block HELP
Input display group number XXX

- Press keys 0, 4 and 1 for "Display group number 41" and confirm entry with Q key.

Indicated on display: (1 to 4 Display zones)

Read Measuring Value Block 41 ->
1 2 3 4

- Check Oxygen sensor heater resistance in display zone 1
Specification: 6.4 to 47.5 Ohm
- Check status of Heated Oxygen Sensor (HO2S) in display zone 2:
Display: Htg.bC.ON

NOTE: The Heated Oxygen Sensor (HO2S) 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.

If the specifications are not attained:







- Remove protective cover -arrows- and separate 4 pin connector (black) to Heated oxygen sensor (HO2S) before catalytic converter -G39-.







- Check probe heating for continuity at Oxygen sensor connector contacts 1 and 2.

If it is determined that probe heating has an open circuit:
- Replace Heated oxygen sensor (HO2S) before catalytic converter - G39-.

If probe heating has continuity:







- Set multimeter to measure voltage and connect to contacts 1 and 2 on connector to control module.
- Start engine and run at idle speed.
- Measure voltage supply:
- When display group 41, display zone 2 displays:
Htg.bC.ON:
Specification: 11.0 to 14.5 V
Display: Htg. bC.ON/Htg.bC.OFF (alternating)
Specification: Between 0.0 to 12.0 V fluctuating switch ignition off.

If no voltage is present:







- Connect test box VAG 1598/22 to control module wiring harness.







- Check wiring between test box and 4 pin connector for open circuit according to wiring diagram.
Contact 2 + socket 27
Wire resistance: Max. 1.5 Ohm

If the specification is obtained:
- Check wiring from contact 1 to Fuel Pump (FP) relay -J17- according to wiring diagram.