Code 45, Oxygen Sensor Circuit Rich Exhaust Indicated: Notes

The ECM supplies a voltage of approximately .43 volt between ECM terminals D6 and D7 (if measurement is taken with a 10-megohm DVOM, reading may be as low as .32 volt). The O2 sensor varies the voltage within a range of about one volt if exhaust is rich and down to about .10 volt if exhaust is lean. When sensor temperature is less than 600°F (316°C), the sensor acts like an open circuit and will not produce voltage. An open sensor circuit or cold sensor causes an open loop condition.

1. Code 45 sets when O2 sensor signal voltage is fixed above .75 volt (750 mV), TPS is more than 3 percent, Codes 21 or 33 are not present, system is in closed loop, coolant temperature is less than 158°F (70°C), and integrator count is not at 128.