Chart C1E - P/S Pressure Switch Signal
The power steering pressure switch is normally open to ground, and circuit No. 495 will be near battery voltage. Turning steering wheel increases power steering oil pressure, and its load on an idling engine. The pressure switch will close before load can cause an idle problem. Closing switch causes circuit No. 495 to read less than one (1) volt. The ECM will increase idle air rate and retard timing. A pressure switch that will not close, or an open circuit No. 495 or 450 may cause engine to stop when power steering loads are high. A switch that will not open, or a circuit No. 450 or 495 shorted to ground, will cause timing to retard at idle and may effect idle quality.
NOTE:
The following step numbers refer to the step numbers in the accompanying Flow Chart.
- Checks for ECM signal voltage on circuit No. 495, and confirms ground circuit No. 450 is okay.
- Maximum resistance, or infinity, indicates an open switch.
- Less than one (1) ohm indicates that switch is closed when power steering pressure is high. Switch is okay.