Air/Fuel Mixture: Adjustments

Test conditions
- No leaks in exhaust system.
- Engine Coolant Temperature (ECT) minimum 85°C (185°F).
- Throttle valve in closed throttle position. Adjust accelerator pedal cable if necessary.
- All electrical consumers switched OFF.
- A/C switched OFF.
- Pressure measuring devices NOT connected.
- Automatic transmission vehicles: selector lever in P or N.

Checking CO Content

NOTE:
CO content cannot be adjusted manually.

- Remove cap screw from exhaust manifold, install adapter VAG 1318/12 and VAG 1732 hose stem.
- Connect CO tester VAG 1363 (or equivalent) with hose adapter VAG 1363/3, according to operating instructions.

NOTE:
CO tester hose adapter must fit tightly over hose stem so that there are no exhaust leaks.

- Check CO content.
^ Specified value: 0.2-1.2% by volume

NOTE:
The following points are to be considered and checked:
^ If the CO content is below 0.2% by volume, there may be leaks around the CO tap tube or the connection to the CO tester.
^ If the CO content is above 1.2% by volume, the cause maybe leaks in the exhaust system between the engine and the heated oxygen sensor.
^ Failure of a spark plug and/or a fouled spark plug causes an increase in the CO content of about 1.7%.

If specified value is not obtained:
- Check DTC memory.

If no malfunctions are stored in DTC memory:
- Activate "Read Measuring Value Block" function 08 with VAG 1551 and read display groups 005 and/or 006, display field 1 (oxygen sensor control).