Code 45 - Rich Exhaust Indication (All Engines)

The ECM supplies approximately .45 volt between terminals "D6" and "D7". (This may read as low as .32 volt, if measured with a 10 megohm digital voltmeter). The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down to about .10 volt if the exhaust is lean. The O2 sensor is like an open circuit and produces no voltage when it is below about 315°C (600°F). An open sensor circuit or cold sensor causes open loop operation. Code 45 is set when the O2 sensor signal voltage at the ECM terminal "D7" remains below .7 volt for 1 minute or more and the system is in closed loop.

1. Grounding the diagnostic terminal with the engine running enables the "Field Service Mode" and allows the ECM to confirm either open or closed loop operation using the "SERVICE ENGINE SOON" light.
2. A steady light or "open loop" indicates the presence of a fault. Grounding circuit 412 causes a low O2 sensor signal voltage. If the ECM and wiring are OK, 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.
3. Check the following if a Code 45 is set: MAF and O2 sensors, high fuel pressure, leaking injectors, canister purge, leaking fuel pressure regulator diaphragm or the TPS. Perform the injector balance test.