Fleetwood Brougham V8-252 4.1L (1985)
Oxygen Sensor: Testing and Inspection
When the oxygen sensor is cold, its output voltage will be approximately .5 volts. The ECM will operate the DEFI system in open loop mode until the
oxygen sensor warms up and its output voltage varies between zero and one volt. When the ECM receives this varying signal from the oxygen sensor, it
will operate the DEFI system in closed loop mode.
Before using this procedure, repair all hard codes other than 13, 44 or 45. If any of these codes have been set, perform the appropriate diagnostic
procedures to verify that the ECM, harness and fuel system are operating properly before replacing the oxygen sensor.
1.
Start engine, enter diagnostics, and display parameter .0.4.
2.
Run engine until coolant temperature reaches 185° F and display parameter .0.7.
3.
If parameter .0.7 indicates no voltage variation, replace oxygen sensor.
4.
If voltage fluctuates below 30 and above 60, observe ``open/closed'' status light above ``off'' button on ECC panel with engine running at fast idle.
If status light illuminates, indicating closed loop operation, oxygen sensor is operating satisfactorily. If status light remains off, indicating open
loop operation, replace oxygen sensor.
5.
If voltage remains between 30 and 60, check for improper or contaminated fuel. If fuel is satisfactory, replace oxygen sensor or repair sensor
electrical connector.
