During handling of the oxygen sensor, do not hit the end of the sensor. The sensor can be easily damaged by impact or rough handling. Additionally, do not allow the sensor to come in contact with water or petroleum products.
The exhaust oxygen sensor or O2S, is mounted in the exhaust stream where it monitors oxygen content in the exhaust gas. The oxygen content in the exhaust is a measure of the air/fuel mixture going into the engine. The oxygen in the exhaust reacts with the oxygen sensor to produce a voltage which is read by the ECM.
- Start the engine and bring it to normal operating temperature, then run the engine above 1200 rpm for two minutes.
- Backprobe with a high impedance averaging voltmeter (set to the DC voltage scale) between the oxygen sensor (02S) and battery ground.
- Verify that the 02S voltage fluctuates rapidly between 0.40-0.60 volts.
- If the 02S voltage is stabilized at the middle of the specified range (approximately 0.45-0.55 volts) or if the 02S voltage fluctuates very slowly between the specified range (02S signal crosses 0.5 volts less than 5 times in ten seconds), the 02S may be faulty.
- If the 02S voltage stabilizes at either end of the specified range, the ECM is probably not able to compensate for a mechanical problem such as a vacuum leak or a high float level (carbureted engines). These types of mechanical problems will cause the 02S to sense a constant lean or constant rich mixture. The mechanical problem will first have to be repaired, then the 02S test repeated.
- Pull a vacuum hose located after the throttle plate. Voltage should drop to approximately 0.12 volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a lean mixture condition. Reattach the vacuum hose.
- Richen the mixture using a propane enrichment tool. Voltage should rise to approximately 0.90 volts (while still fluctuating rapidly). This tests the ability of the 02S to detect a rich mixture condition.
- If the 02S voltage is above or below the specified range, the 02S and/or the O2S wiring may be faulty. Check the wiring for any breaks, repair as necessary and repeat the test.
REMOVAL & INSTALLATION
See Figures 1 through 5
- Disconnect the negative battery cable.
- Ensure that the engine and exhaust pipes are cold. Locate the oxygen sensor. Some sensors are on the front pipe others are on the catalyst, you may have more than one.
- Spray a lubricant on the studs to ease removal.
- Disconnect the negative battery cable and disconnect the oxygen sensor wiring.
- Remove the oxygen sensor retaining nuts.
- Remove the oxygen sensor and gasket.
- Install the oxygen sensor with a new gasket.
- Apply a coating of anti-seize to the studs. Install the nuts and tighten to 14 ft. lbs. (20 Nm).
- Connect the oxygen sensor wiring.
- Connect the negative battery cable.