Checking Control Unit ResponseIf, in the test above, the multimeter shows little or no fluctuation, check the control unit's response to a dramatic change in signal from the oxygen sensor. With the ignition off and the test harness connected, disconnect the harness connector from the coolant temperature sensor and bridge the connector terminals. See Fig. 5-6. Disconnect the green oxygen sensor wire.
Turn the ignition on. Differential pressure regulator current should be 9 to 11 mA. Ground the oxygen sensor connector (at the end of the green wire). After about 20 seconds, the current should increase to 19 to 20 mA. Correct measured values confirm that the control unit is responding normally, and if the differential pressure regulator current still does not fluctuate when tested as described above, the oxygen sensor or its wire is faulty and should be replaced. If the current reading does not increase to 19 or 20 mA when the oxygen sensor wire is grounded, turn off the ignition and check for continuity between the green oxygen sensor wire and terminal 8 of the control unit connector. If there is no continuity, the wiring between the oxygen sensor and the control unit is faulty. Repair as necessary and repeat the test. If there is continuity and the control unit is still not responding when the oxygen sensor wire is grounded, then the control unit is faulty and should be replaced. |