Escort L4-110 1.8L DOHC (1994)
Oxygen Sensor: Testing and Inspection
Component Tests
CAUTION: Use ONLY a high impedance Digital Volt Ohm Meter (DVOM) when testing components on computerized vehicles.
Set voltmeter to read VOLTS only (not ohms). Be sure external voltage is not applied to sensor lead; sensor damage may occur.
1. Make sure vehicle is at normal operating temperature. Run engine at 2500 RPM for 3 minutes.
2. With engine OFF, connect negative voltmeter terminal to engine ground. Set meter to 2 volts DC. Unplug oxygen sensor lead. Connect voltmeter
positive lead to sensor.
3. Create full lean condition for 10 seconds; voltage should decrease to 0.2 volts or less and remain there.
4. Create full rich condition for 10 seconds; voltage should increase to 0.8 volts or more and remain there.
5. If sensor voltage fails to vary according to test, it is defective.
6. Reconnect sensor and clear codes.
