DTC 45

Code 45 Chart:

Code 45 Wiring Diagram:

CIRCUIT DESCRIPTION:

The Electronic Control Module (ECM) supplies a voltage of about 0.45 volt between terminals "D6" and "D7". (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 volt if the exhaust is rich, down through about 0.10 volt if exhaust is lean. 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.

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to ECM CONNECTOR IDENTIFICATION under ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS for correct color code identification of circuit.

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

1. Code 45 is set when the O2 sensor signal voltage or CKT 412:

^ Remains above 0.7 volt for 30 seconds; and in "Closed Loop"
^ Engine time after start is 1 minute or more
^ Throttle less than 1/2 open but not at idle

DIAGNOSTIC AIDS:

^ Using the "Scan", observe the block learn values at different rpm and air flow conditions. If the conditions for Code 45 exists, the block learn 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, a Code 45 may be set. See CHART A-7.

^ Rich Injector. Perform injector balance test CHART C-2A.

^ Leaking Injector. See CHART A-7.

^ Check for fuel contaminated oil.

^ High Energy Ignition (HEl) Shielding. An open ground CKT 453 (ignition system low reference signal) may result in Electro Magnetic Interference (EMI), or 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.

^ Check fuel vapor canister for fuel saturation. If full of fuel, check canister control and hoses.

^ A Mass Air Flow (MAF) Sensor. An output that causes the ECM to sense a higher than normal air flow 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 the rich condition is gone while the sensor is disconnected or use tool J-36101 and test MAF sensor.

^ Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for fuel.

^ An intermittent Throttle Position Sensor (TPS) output will cause the system to go rich, due to a false indication of the engine accelerating.

^ An EGR staying open (especially at idle) will cause the 02 sensor to indicate a rich exhaust.