Action Taken
- ECM turns on "ENGINE CONTROL SYSTEM FAULT" light.
- ECM commands BCM to display "SERVICE SOON" message on DIC.
- ECM turns off canister purge and air management solenoids.
- ECM uses left oxygen sensor input information for air/fuel computations.
The ECM provides a .45-volt reference signal to oxygen sensor on circuit No. 412. When oxygen sensor is cold (below 392°F/200°C), output voltage will be about .45 volts and ECM will keep system in open loop operation. When warm, a properly operating oxygen sensor will drive the .45-volt reference lower (below .45 volts) to indicate a rich mixture. Oxygen sensor signal voltage will swing from rich to lean rapidly. This will occur at least one swing every 2 seconds if ECM is in good control of air/fuel mixture.
When ECM sees that oxygen is not at cold voltage of .45 volts, it will send system into closed loop operation. In closed loop operation, ECM will meter fuel into engine based on oxygen sensor readings.
Code EO45 will set when right oxygen sensor stays at rich voltage for more than 50 seconds during test conditions. Code EO45 will also set when:
- Oxygen sensor circuitry has faults.
- Air-fuel ratio is actually rich due to fuel control or emission system fault.
- With oxygen sensor disconnected, parameter ED33 should remain at reference voltage (.38-.63 volts).
- Checks for ECM able to recognize lean oxygen sensor input.
- The ECM compares oxygen sensor signal voltage received on circuit No. 412, to ground voltage on circuit No. 413. If ECM does not have a good ground to engine on circuit No. 413, oxygen sensor can appear falsely high or low.
With engine running, use voltmeter to measure voltage from oxygen sensor pin "A" to ECM terminal "E15". If voltage is -.05 to +.05 volts, ground is okay. If voltage is less than -.05 volts or greater than +.05 volts, repair poor ground on circuit between ECM terminal "E15" and engine ground.