Powertrain Controls - ECM/PCM

Code 45:

Oxygen Sensor Circuit Diagram:

CIRCUIT DESCRIPTION:

The PCM supplies a voltage of about 0.45 volt (450 mV) between terminals "BD3" and "BD2." (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt.) The 02 sensor varies the voltage within a range of about 1.0 volt (1000 mV) if the exhaust is rich, down through about 0.10 volt (100 mV) 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.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 45 is set when the 02 sensor signal voltage on CKT 412:

^ Remains above 0.75 volt for 2.0 minutes while in "Closed Loop".
^ Throttle angle between 0.6 and 1.9 volts.


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 code 45 may be set. See fuel system diagnosis CHART A-7.
^ Rich Injector - Perform injector balance test CHART C-2A.
^ Leaking Injector - See CHART A-7.
^ 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.
^ TPS - An intermittent TPS output will cause the system to go rich, due to a false indication of the engine accelerating.
^ False rich indication due to silicon contamination of the O2 sensor. This will be indicated by a code 45 accompanied by lean driveability conditions and a powdery white deposit on the sensor.