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Oxygen Sensor

  1. Unplug oxygen sensor connector. Start engine and run for 2 minutes at 3000 RPM under no load. Raise engine speed to 4000 RPM and release throttle suddenly at least 5 times.
  2. Within one minute after engine has been warmed up, measure voltage between connector terminal and body ground as outlined in steps 3) and 4).
    NOTE: If it takes more than one minute to complete checks, warm-up engine as outlined in step 1.
  3. Raise engine speed to 5000 RPM, and lower to 2000 RPM. Immediately turn ignition off. Voltage at terminal should be less than 0.4 volts. Disconnect vacuum hose No. 21 (hose between throttle body and MAP sensor on Civic CRX Si and Prelude), at throttle body. Plug throttle body fitting.
  4. Connect vacuum pump to open end of vacuum hose. Apply 12 in. Hg vacuum and raise engine speed to 4000 RPM. Voltage reading should be above 0.6 volts. Replace O2 sensor if voltages are not within specifications.
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