Accord 1985-86 and Prelude 1986-89
1. Remove the oxygen sensor connector.
2. Start the engine and warm it up with no load at 3000 RPM, then increase the RPM to 4000 RPM and quickly release the throttle pedal. Repeat the procedure at least 5 times.
3. Within a minute after the engine warms up, measure the voltage between the connector terminal and the ground wire, it must correspond to that described in points 4 and 5.
If the measurement procedure takes more than one minute, then repeat the engine warm-up as indicated in the second paragraph.
4. Increase the engine speed to 5000 rpm, then reduce it to 2000 rpm by using the accelerator pedal, immediately turn off the ignition - at this moment the voltage should be no more than 0.4 V.
5. Disconnect the vacuum hose between the manifold air pressure sensor and the throttle from the throttle and plug the hose hole in the throttle. Connect a hand pump to the open end of the hose, apply a vacuum of 300 mmHg. and increase the engine speed to 4000 rpm. The voltage must be at least 0.6 V.
6. If the voltmeter readings are not as described, replace the oxygen sensor.