DTC 45

Code 45 Diagnostic Chart:

Code 45 Circuit Diagram:

CIRCUIT DESCRIPTION:

The ECM supplies a voltage of about 0.45 volt between terminals "3" and "20" of the ECM. (If measured with a 10 Meg ohm digital voltmeter, this may read as low as 0.32 volts.) The O2 sensor varies the voltage within a range of about 1 volt, if the exhaust is rich, down to about 0.10 volt, 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.

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

1. Code 45 is set, when the 02 sensor signal voltage in circuit 412:

^ Remains above 0.6V for 2 minutes or more.
^ System operating in "CLOSED LOOP."
^ 02 sensor must reach a temperature of 360°C (600°F).
^ Engine running 5 minutes or more, at part throttle.

DIAGNOSTIC AIDS:

The Code 45, or rich exhaust, is most likely caused by one of the following:

^ If the M/C solenoid does not click with ignition "ON" and "ALDL" terminal grounded, and there is no Code 23, check for sticking solenoid.
^ EEC - Check for fuel saturation. If full of fuel, check canister control and hoses, refer to EVAPORATIVE EMISSION CONTROL under EMISSION CONTROLS.
^ MAP Sensor 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 that the engine is accelerating.
^ 02 Sensor Contamination - Inspect Oxygen Sensor for silicone contamination from fuel or use of improper RTV sealant. The sensor may have a WHITE, powdery coating resulting 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 and driveability problem. If Code 45 is intermittent, Testing and Inspection
^ If the EGR valve is stuck open it may cause a rich exhaust indication and could possibly set a Code 45, especially at idle.
^ Faulty Reed Valve in AIR System.