Code EO45, Rich Exhaust Indication
The ECM supplies a signal voltage of about .45 volt between terminals No. D7 and D6. (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, down through about .10 volt if exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below about 600°F (360°C). An open sensor circuit or cold sensor causes "open loop" operation.
Code EO45 is set when oxygen sensor signal voltage at the ECM "C-D" connector terminal No. D7 remains above .75 volt for 2 minutes and time since engine start is one minute or longer. The engine must be in "closed loop" mode for the above conditions. This does not cause the fuel integrator to reset to 128.
- Entering "Diagnostic Mode" allows the ECM to confirm either "open" or "closed loop" operation using data parameter ED15. This also allows the oxygen sensor to be monitored.
- A steady light or "open loop" indicates the fault is present. Grounding circuit No. 412 causes a low oxygen sensor signal voltage. If the ECM and wiring are okay, the ECM should recognize the low voltage and confirm the lean signal by turning off the "SERVICE ENGINE SOON" light for at least 15 seconds.
- Diagnostic Aids
- A Code EO45 will not be caused by a faulty oxygen sensor. Code EO45 indicates a rich exhaust and diagnosis should begin with the following items:
- A silicon contaminated oxygen sensor will cause a steady signal above .55 volts and set Code EO45.
- Fuel Pressure. System will go rich if pressure is too high. The ECM can compensate for some increase. However if it gets too high, a Code EO45 may be set.
- Leaking fuel pressure regulator or leaking fuel injector.
- Canister Purge. Check for fuel saturation. If full of fuel, service purge system.
- MAF Sensor. An output that causes the ECM to sense a higher than normal manifold airflow can cause the system to go rich. Disconnecting the MAF sensor will allow the ECM to set a fixed value for the MAF sensor. Substitute a different MAF sensor if the rich condition is gone while the sensor is disconnected.
- TPS. An intermittent TPS output will cause the system to go rich, due to a false indication of the engine accelerating.