Powertrain Controls - ECM/PCM

Code Chart 45:

Oxygen Sensor Wiring Circuit:

Circuit Description:
The Engine Control Module (ECM) supplies a voltage of about .45 volt between terminals "C7" and "C8". (If measured with a 10 megohm digital voltmeter, this may read as low as .32 volt.)

When the O2S reaches operating temperature, it varies this voltage from about .1 volt (exhaust is lean) to about .9 volt (exhaust is rich),

The sensor is like an open circuit and produces no voltage when it is below 316°C (600°F). An open sensor circuit or cold sensor causes "Open Loop" operation.

DTC 45 Will Set When:
^ The Oxygen Sensor (O2S) signal voltage on CKT 412 remains above .55 volt.
^ System is operating in "Closed Loop."
^ Engine run time after start is 2 minutes or more.
^ Throttle angle is greater than 5%.
^ These conditions exist for 51 seconds or more.

Action Taken (ECM will default to): Malfunction Indicator Lamp (MIL) illuminates.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step determines if DTC 45 is the result of a hard failure or an intermittent condition.

Diagnostic Aids: DTC 45, or rich exhaust, is most likely caused by one of the following:
^ 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 DTC 45 will be set. Refer to "Fuel System Diagnosis" CHART A-7. Related Tests, Information and Procedures
^ Leaking Injector - Refer to CHART A-7. Related Tests, Information and Procedures
^ An Open Ground CKT 153 - May result in induced electrical "noise." The ECM interprets this "noise" as reference pulses. The additional pulses result in a higher than actual engine speed signal. The ECM then delivers too much fuel causing the system to go rich. The engine tachometer will also show higher than actual engine speed, which can help in diagnosing this problem.
^ Canister Purge - Check for fuel saturation. if EVAP canister is full of fuel, check EVAP canister control valve and hoses. Refer to "Evaporative Emission (EVAP) Control System." Evaporative Emissions System
^ MAP Sensor - An output that causes the ECM to sense a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the Manifold Absolute Pressure (MAP) sensor will allow the ECM to set a fixed value for the MAP sensor. Substitute a different MAP sensor if the rich condition is gone, while the sensor is disconnected.
^ TP Sensor - An intermittent Throttle Position (TP) sensor output will cause the system to operate rich due to a false indication of the engine accelerating.
^ Oxygen Sensor (O2S) Contamination - Inspect O2S for silicone contamination from fuel or use of improper RTV sealant. The sensor may have a white, powdery coating and result in a high but false signal voltage (rich exhaust indication). The ECM will then reduce the amount of fuel delivered to the engine causing a severe surge driveability problem.
^ EGR Valve - Exhaust Gas Recirculation (EGR) sticking open at idle is usually accompanied by a rough idle and/or stall condition.
If DTC 45 is intermittent, refer to "Diagnosis By Symptom." Testing and Inspection
^ Engine Oil Contamination - Fuel fouled engine oil could cause the O2S to sense a rich air/fuel mixture and set a DTC 45.
^ Engine Coolant Temperature (ECT) Sensor - Check coolant sensor using "Diagnostic Aid" on DTC 14 chart. Powertrain Controls - ECM/PCM