DTC 45

Code 45 Chart:

Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION:
The ECM supplies a voltage of about 0.45 volts between terminals "C7" and "C8." (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts). When the oxygen sensor reaches operating temperature, it varies the voltage within a range of about .1 volt if the exhaust is lean, to about 0.9 volt if exhaust is rich. The sensor is like an open circuit and produces no voltage when it is below about 316°C (600°F). An open sensor circuit or cold sensor causes "OPEN LOOP" operation.

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

1. Code 45 is set when the oxygen sensor signal voltage on circuit 412 remains above 0.55 volt under the following conditions:

^ System is operating in "CLOSED LOOP."
^ Engine run time after start is 120 seconds or more.
^ Throttle angle is greater than 5%.

DIAGNOSTIC AIDS:
Code 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 Code 45 may be set. Related Tests, Information and Procedures
^ Leaking Injector - Related Tests, Information and Procedures
^ HEI Shielding - An open ground circuit 153 (ignition system reference low) may result in induced electrical "noise." The ECM looks at 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 system to go rich. Engine tachometer will also show higher than actual engine speed which can help in diagnosing this problem.
^ Canister Purge - Check for fuel saturation. If full of fuel, check canister control and hoses. Chart C-3 Evaporative Emission Control 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 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.
^ TPS - An intermittent TPS output will cause the system to go rich, due to a false indication of the engine accelerating.
^ Oxygen sensor contamination - Inspect the oxygen sensor 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 - A valve sticking open at idle, usually accompanied by a rough idle, stall complaint. If a Code 45 is intermittent, Testing and Inspection
^ Engine Oil Contamination - Fuel fouled engine oil could cause the O2 sensor to sense a rich air/fuel mixture and set a Code 45.