Code 45: Rich Exhaust Indication: Notes

The ECM supplies a voltage of about .45 volt between terminals No. E14 and E15. If measured with a 10-megaohm digital voltmeter, this may read as low as .32 volts. The oxygen sensor varies the voltage within a range of about one volt. If the exhaust is rich, voltage will go down about .10 volts. If exhaust is lean, voltage will go up about .20 volts. When the oxygen sensor temperature is below 600°F (360°C), it is like an open circuit and produces no voltage. An open sensor circuit, or cold sensor, causes "open loop operation".

1. Code 45 is set when the oxygen sensor signal voltage on circuit No. 412 remains above .7 volt for 30 seconds or more. When system is in "closed loop", engine time after start is one minute or more or throttle angle is between 2 and 20%, will also set Code 45. Code 45, or rich exhaust can be caused by the following:
   • Fuel system will go rich, if pressure is too high. The ECM can compensate for some increase. However, if it gets too high, a Code 45 will be set.
   • Fuel system will go rich, if a fuel injector leaks.
   • An open ground in circuit No. 453 may result in EMI, or induced electrical noise. The ECM looks at this noise as reference pulses. The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel, causing system to go rich.