PFI Chart A-6, Oxygen Sensor Test
PCM provides a .45-volt reference to oxygen sensor. When warm, a properly operating oxygen sensor will drive .45-volt reference lower (less than .45 volt) to indicate lean mixture and higher (more than .45 volt) to indicate rich mixture.
The oxygen sensor must be able to generate a counter voltage of greater than .15 volt or less than .45-volt reference to cause PCM to register a cross count of rich to lean or lean to rich. The oxygen sensor must generate cross counts to enable the system to go to closed loop operation.
The oxygen sensor test checks that the PCM is receiving voltage signals of sufficient range from the sensor to generate a cross count.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- PCM trouble Code EO13, EO44 and EO45 are designed to detect a sensor fault. The slow reaction time of the sensor may cause a driveability problem. PCM data ED32 and ED33 will display oxygen sensor voltage. With engine at normal operating temperature, O2 sensor voltage should be constantly changing. A fixed voltage at zero volts, indicate a shorted circuit No. 412 the right O2 sensor and circuit No. 912 the left O2 sensor. A fixed voltage between .42-.48 volt, indicate an open in circuits No. 412 or No. 413 the right O2 sensor and circuits No. 413 or No. 912 the left O2 sensor.
- If the system cannot go to closed loop operation, both the O2 sensors are not functioning.