DTC 45

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

Oxygen Sensor Wiring Circuit:

Circuit Description:

The ECM supplies a voltage of about .45 volt (450 mV) between terminals "YE14" and "YE15." (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.) The O2S varies the voltage within a range of about 1 volt (1000 mV) if the exhaust is rich, down through 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). An open sensor circuit or cold sensor causes "Open Loop" operation.

DTC 45 is set if the O2S signal voltage on CKT 412:
^ Remains above .75 volt for 2 minutes while in "Closed Loop."
^ Throttle angle between 3.5% and 40%.
^ No DTC 21 or DTC 22.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

1. Running the engine at 1200 RPM keeps the 02S hot, so an accurate display voltage is maintained. Opening the 025 wire should result in a voltage display of between 350 and 550 mV. If the display is still fixed below 350 mV, the fault is a short to ground in CKT 412 or the ECM is faulty.

Diagnostic Aids:

Using the Tech 1 observe the long term fuel trim values at different RPM and air flow conditions. The Tech 1 also displays the fuel trim cells, so the long term fuel trim values can be checked in each of the cells to determine when the DTC 45 may have been set. If the conditions for DTC 45 exist, the long term fuel trim values will be around 115.

^ Fuel Pressure. System will go rich if pressure is too high. The ECM can compensate for some Increase. However, if it gets too high, 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.
^ EVAP Canister Purge. Check for fuel saturation. If full of fuel, check canister control and hoses. See "Canister Purge in Evaporative Emission (EVAP) Control System".
^ MAF Sensor. An output that causes the ECM to sense a higher than normal airflow can cause the system to go rich. Disconnecting the MAF sensor will allow the ECM 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 engine accelerating.
^ False rich indication due to silicone contamination of the Oxygen Sensor (O2S). This will be indicated by DTC 45 accompanied by lean driveability conditions and a powdery white deposit on the sensor.