Oxygen Sensor (O2S) Testing

VISUAL INSPECTION
- Connectors and wires
- Housing and insulator for cracks/damage
- Sensor tip for silicone contamination (white powdery coating)

CAUTION: Do NOT perform the following test for more than 2 minutes, as this may cause damage to the catalytic converter.

PERFORMANCE TEST
Checks working range and response (speed).
- Warm engine
- Install DVOM between sensor and ground (2 volt D.C. range)
- "RUN" engine at steady cruise speed (about 2500 rpm)
Voltage should vary at least eight times in ten seconds between 0.2 and 0.8 volts (normal range).
- Drive system rich: The use of a properly adjusted propane flow-meter (J-26911) is industry standard.
Voltage should increase to at least 0.8 volts within two to three seconds.
- Drive system lean: Create a vacuum leak from a source that is not an control module input or output.
Voltage should drop to at least 0.3 volts within two to three seconds.
NOTE: After each test the O2 sensor should return to normal operating range within two to three seconds.
- O2 Sensor should be replaced for failure to pass any of the tests above.
NOTE: A CEC system that is operating excessively rich or lean will drive the 02 sensor to its maximum range and should be repaired first and not diagnosed as a 02 sensor failure.
- Reconnect all hoses and electrical connectors. Clear all codes set and retrain idle.

HEATING ELEMENT (H20S only)
- Turn ignition "OFF." Disconnect electrical connector.
- Connect test light between harness terminals "A" and "B."
- Turn ignition "ON." Test light should be "ON."
- If test light is "OFF," connect test light to harness terminal "A" to ground. Light should be "ON" ensuring power circuit is operating correctly.
- Turn ignition "OFF."
- Using an ohmmeter, measure resistance between terminals A and B.

Resistance @ Specified Temperature
3.5 ohms @ 20°C (68°F)
14 ohms @ 350°C (662°F)