Oxygen Sensor: Testing and Inspection
HEATED OXYGEN SENSOR AND OXYGEN SENSOR CONTROLRequirements
^ Idle speed check OK.
^ Exhaust system must be leak tight between the three-way catalytic converter and the cylinder head.
Procedure
- Connect VAG 1551 Scan Tool (ST).
- Start engine and let idle.
- Select function 08 "Read measurement block".
^ Display will appear as shown:
Read measurement block 1
1 2 3 4
- Only continue with test if coolant temperature is over 85°C (185°F) in channel 1.
- Let engine idle for two minutes longer.
- Connect CO tester to CO tap tube using adaptor VAG 1363/3.
- Measure CO content.
^ Specification: 0.3 - 1.2 vol.%
- Read oxygen sensor voltage in channel 3.
^ Display will appear as shown:
Read measurement block 1
1 2 3 4
^ Specification: 0.0 - 0.75 Volts (fluctuating)
- Disconnect vacuum hose from fuel pressure regulator (arrow).
NOTE: Value must increase then drop back to original value.
- Press --> button.
- Press 0 and 6 buttons to select function 06 "end data transfer".
- Press Q button to enter input.
- If specified values NOT obtained:
- Check voltage supply for oxygen sensor heating.
- Perform electrical testing. Refer to Diagnostic Charts / Electrical Test Steps (ECM Pinout) / Test Steps 16 and/or 32. Testing and Inspection
- Replace Heated Oxygen Sensor (HO2S) (G39).