Understand how Honda oxygen sensors work. A rich fuel mixing with little oxygen in the exhaust leads to a typical voltage of 0.8 to 0.9 through the sensor's platinum electrodes. A lean fuel mixture with more oxygen in the exhausts causes the voltage to drop 0.1 to 0.3 volts. A balanced air and fuel mixture averages around 0.45 volts.
Check your oxygen sensors regularly. Honda oxygen sensors usually last at least 50,000 miles (80,000 km), but older cars, or contaminated sensors, may affect their ability to reduce emissions. The sensors should be checked at these intervals: Unheated oxygen sensors (1976 to early 1990 models): Every 30,000 to 50,000 miles (48,000 to 80,000 km). The first generation of heated oxygen sensors (mid-1980s to mid-1990s): Every 60,000 miles (97,000 km). The second generation of heated oxygen sensors (since the mid-1990s): Every 100,000 miles (160,000 km).
Find out how many Honda oxygen sensors your vehicle has. Some vehicles introduced two Bosch oxygen sensors on V6 and V8 engines in the late 1980s. The number of Honda oxygen sensors doubled when Onboard Diagnostics II was developed in the mid-1990s. Check for extra oxygen sensors near the catalytic converter.
Test your Bosch oxygen sensors if you've been using leaded gasoline, have a problem with coolant leaks or frequently add oil to your car. A Honda oxygen sensor may fail if it becomes contaminated by silicone (from gasket sealers), phosphorus or lead. Check oxygen sensors for other causes of failure, including mechanical stress or environmental factors such as road splash.
Pay attention to any of the following signs of trouble coupled with a check engine light on the dashboard: Emissions test failure. Drivability issues, such as hesitation. Increased fuel consumption.
Borrow or purchase a good quality digital voltmeter. Analog voltmeters don't work well enough to check oxygen sensors.
Connect the positive lead of the voltmeter to the sensor output wire.
Attach the negative lead to the accessory bracket or clean engine block.
Turn the key without starting the engine. Check the connections and repeat the process if you don't see a change in the voltage.
Start the car and run the engine at at least 2,000 RPM for a few minutes to warm up the sensor. You may need to rev the engine a few times. Look for several cross counts (passing the 0.45 volt mark) per second. This indicates closed looped operation and tells you the engine is warm enough.
Look for rapid voltage changes from 0.2 to at least 0.7. If this occurs, the Honda oxygen sensor is good. If the voltage stays steady below 0.45, it is steady low. If the voltage stays steady above 0.45, it is steady high. Allow air to enter the PCV valve. If this moves the voltage to less than 0.3, the sensor is probably good.
Unplug the voltmeter if you don't see the correct voltage changes. Reattach and repeat the steps. You have a bad oxygen sensor if there are still no rapid voltage changes.
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