Oxygen Sensor
- Ensure engine is at operating temperature. Ensure idle speed adjustment, and voltage to O2 sensor heater and coolant temperature sensor are correct.
- Connect voltmeter to differential pressure regulator using Adapter (VW 1315A/1). See Fig 1
. Start engine and let idle for 2 minutes. Note control voltage at differential pressure regulator.
- Remove a manifold vacuum hose to induce lean mixture. Control voltage should increase. If not, disconnect O2 sensor wire connector. Ground harness end for 20 seconds and recheck control voltage. If control voltage increases, replace O2 sensor.
- If not, check wire harness for opens or shorts to ground or power. If wire harness is okay, replace ECU.
Courtesy of AUDI OF AMERICA, INC.