DTC 45

Code 45 - Rich Exhaust Indicated:

Wiring Diagram For Code 45 - Rich Exhaust Indicated:

CIRCUIT DESCRIPTION
The Electronic Control Module (ECM) supplies a voltage of about 0.45 volts between terminals "D6" and "D7". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts.) The oxygen sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volts if exhaust is lean.
The sensor is like an open circuit and produces no voltage when it is below about 315° 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 oxygen sensor signal voltage or circuit 412:
^ Remains above 0.7 volts for 50 seconds, and in "Closed Loop".
^ Engine time after start is 1 minute or more.
^ Throttle angle greater than 2%. (about 0.2 volts above idle voltage)

DIAGNOSTIC AIDS
Using the "Scan" tool, observe the block learn values at different RPM and air flow conditions. The "Scan" tool also displays the block cells, so the block learn values can be checked in each of the cells to determine when the Code 45 may have been set. 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. Refer to Chart A-6 Fuel System Pressure Test.

Leaking Injector
Refer to chart A-4 Injector Circuit Diagnosis.
Also check for fuel contaminated oil.

High Energy Ignition (HEI) Shielding
An open ground circuit 453 (ignition system reference low) may result in Electromagnetic Interference (EMI). 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.

Manifold Absolute Pressure (MAP) Sensor
An output that causes the ECM to sensor 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.

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