Code 45, O2 Sensor CKT/Rich Exhaust Indicated

ECM supplies a voltage of approximately .43 volt between ECM terminals D6 and D7. If voltage is measured with a 10-megohm DVOM, reading may be as low as .32 volt. The O2 sensor varies the voltage within a range of .1 volt (lean exhaust) to 1 volt (rich exhaust). When sensor temperature is less than 600°F (316°C), the sensor acts like an open circuit and will not produce voltage. A cold sensor, or open sensor circuit, causes open loop condition.

1. Code 45 is set when O2 sensor signal voltage is fixed above .75 volt (750 mV), TPS is more than 3 percent, Codes 21 and 33 are not present, system is in closed Loop, coolant temperature is less than 155°F (68°C), and integrator count is not at 128.