Calais L4-151 2.5L VIN U TBI (1989)
The Power Steering Pressure Switch (PSPS) is normally open to ground, and circuit 495 will be near battery voltage. Turning the steering wheel
increases power steering oil pressure, and engine load. This causes the idle speed to change. The pressure switch will close before the engine load can
cause an idle problem. Closing the switch causes circuit 495 to read less than 1 volt, and the ECM will increase the idle air rate. A pressure switch that
will not close or an open circuit in 495 or 450, may cause the engine to stall at idle when power steering loads are high. A switch that will not open or
circuit 495 shorted to ground, may affect idle quality.
TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.
1.
Different "Scan" tools may display the state of this switch in different ways. A SCAN tool that produces faulty readings should NOT be used, and
the problem should be reported to the tool manufacturer. Use of a faulty SCAN tool can result in improper diagnosis and unnecessary component
replacement. Follow the proper instructions, located in the owners manual, for the specific SCAN tool being used.
2.
This checks if circuit 495 is shorted to ground.
3.
This step should simulate a closed switch.
