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Post by steveX » Sun Apr 20, 2008 5:22 pm

CIRCUIT DESCRIPTION:The ECM supplies a voltage of about .45 (450 mV) between terminal (purple wire) and (tan wire). IF MEASURED WITH A 10 MEGOHM DIGITAL VOLTMETER, THIS MAY READ AS LOW AS .32 VOLT.) The o2 sensor varies the voltage within a range of about 1 volt (1000 mV) if the exhaust is rich, down throgh about .10 volt (1000 mV) if exhaust is lean. The sensor is like an open circuit and produces no voltage when it is below about 360 degree C (600F). An open sersor circuit or cold sensor causes "open loop" operation.

Test Description:Number(s) refer to circled number(s) on the diagnostic chart.
1. code 45 is set when the o2 sensor signal voltage or (purple wire)

* Remain above .75 volt for 2 minutes and in "

DIAGNOSTIC AIDS:Using the "scan," observe the block learn values at different rpm and air flow conditions. The "scan" 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

* RICH INJECTOR Perform injector balance test

* check for fuel contaminated oil.
* CANISTER PURGE Check for fuel saturation. If full of fuel, check canister control and hoses. (EECS) "Evaporative Emission Control System"

* MAF SENSOR An output that causes the ECM to sense a higher than normal airflow 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 rich condition is gone while the sensor is disconnected.

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

* TPS An intermittent TPS output will cause the system to go rich due to a false indication of the engine acceleration.

* EGR An EGR staying open (especially at idle) will cause the O2 sensor to indicate a rich exhaust and this could result in a code 45.

1989 buick lesabre

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