With VAG

CHECKING OXYGEN SENSOR AND OXYGEN SENSOR CONTROL

NOTE: Test using VAG 1551 Scan Tool (ST) with engine idling.

REQUIREMENTS
^ Engine basic setting OK.
^ Exhaust system not leaking between Three Way Catalytic Converter (TWC) and cylinder head.
^ Voltage supply for Heated Oxygen Sensor (HO2S) heater circuit OK.
^ VAG 1551 Scan Tool connected with "Read Measuring Value Block" function (08) selected (display group number 1).

PROCEDURE

^ Indicated on display (1 - 4 = display fields)

Read measuring value block 1 -->
1 2 3 4

- Continue testing only when:

^ Engine Coolant Temperature (ECT) is over 80°C (176°F) - display field 2.
^ Engine has run 2 minutes at idle.

- Read Oxygen Sensor factor in display field 3.

^ Specified value: display fluctuates.

- If value in display field 3 does not fluctuate:

- Briefly accelerate and repeat test.
- Press --> button.
- Press buttons -0- and -6- to select the "End Output" function.
- Press -Q- to confirm input.




- If Oxygen Sensor factor 1.00 does not change even during acceleration:

- Disconnect connector -1- from Engine Coolant Temperature Sensor -2-.
- Press buttons -0- and -5- to select the "Erase DTC Memory" function.
- Press -Q- to confirm input.



- Unplug connector for Heated Oxygen Sensor.
- Connect adapter lead from VW 1594 to cavity 4 (wiring to Motronic Engine Control Module (ECM) (J220) and hold to Ground (GND).
- Value in display field 3 must increase.

- If value increases:

- Replace Heated Oxygen Sensor.

- If value does not increase:

- Perform electrical testing.
- If necessary replace Motronic Engine Control Module.
- Connect Engine Coolant Temperature Sensor.
- Press --> button.
- Press buttons -0- and -5- to select the "Erase DTC Memory" function.
- Press -Q- to confirm input.
- Press --> button.
- Press buttons -0- and -6- to select the "End output" function.
- Press -Q- to confirm input.