DTC 45

DTC 45 - Oxygen Sensor (O2S) Circuit (Rich Exhaust Indicated):

Oxygen Sensor (O2S) Wiring Circuit:

Circuit Description:

The PCM supplies a voltage of about .45 volt (450 mV) between terminals "BD3" and "BD2". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.) The 02S varies the voltage within a range of between about 1 volt (1000 mV) if the exhaust is rich, to about .10 volt (100 mV) if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is below about 360°C (600°F). A DTC 44, 45 or an open sensor circuit or cold sensor causes "Open Loop" operation.

DTC 45 is set when the 02S signal voltage on CKT 412:
^ Remains above .75 volt for 2 minutes while in "Closed Loop."
^ Throttle angle between 6% and 40%.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. Determines if conditions necessary to set DTC 45 exist.

Diagnostic Aids:

^ Fuel Pressure System will go rich if pressure is too high. The PCM can compensate for some increase. However, if it gets too high, a DTC 45 may be set. Related Tests, Information and Procedures
^ Rich Injector - Chart C-2A Fuel Injector Balance Test
^ Leaking Injector - Related Tests, Information and Procedures
^ Check for fuel contaminated oil.
^ Canister Purge - Check for fuel saturation. If full of fuel, check canister control and hoses.
^ MAF Sensor - An output that causes the PCM to sense a higher than normal airflow can cause the system to go rich. Disconnecting the MAF sensor will allow the PCM to set a fixed value for the sensor. Substitute a different MAF sensor if the rich condition is gone while the sensor is disconnected.
^ Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for fuel.
^ TP Sensor - An intermittent TP sensor output will cause the system to go rich due to a false indication of the throttle moving.
^ False rich indication due to silicon contamination of the oxygen sensor. This will be indicated by a DTC 45 accompanied by lean driveability conditions and a powdery white deposit on the sensor.