Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1985S10/T10 BLAZER 4WD L4-151 2.5LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSPOWER STEERING PRESSURE SWITCHTESTING AND INSPECTION
1985 Chevrolet S10/T10 Blazer 4WD L4-151 2.5L
Power Steering Pressure Switch: Testing and Inspection
1985 Chevrolet S10/T10 Blazer 4WD L4-151 2.5LSECTION Testing and Inspection
Chart C-1E - Power Steering Pressure Switch Check:
Wiring Diagram For Chart C-1E - Power Steering Pressure Switch Check:
CHART C-1E - POWER STEERING (P/S) PRESSURE SWITCH CHECK
Circuit Description:
The power steering pressure switch is normally open to ground, and circuit 495 will be near battery voltage.
Turning the steering wheel increases power steering oil pressure and its load on an idling engine. The pressure switch will close before the load can cause an idle problem.
Closing the switch causes circuit 495 to read less than 1 volt. The ECM will increase the idle air rate and retard the timing.
^ A pressure switch that will not close, or an open CKT 495 or 450, may cause the engine to stop when power steering loads are high.
^ A switch that will not open, or a CKT 450 or 495, shorted to ground, will cause timing to retard at idle, and may affect idle quality.
Test Description:
1. Checks for ECM signal voltage on CKT 495 and confirms that ground CKT 450 is OK.
2. Maximum resistance, or infinity, indicates an open switch.
3. Less than 1 ohm indicates that the switch is closed when the power steering pressure is high. Switch is OK.
RENDER: 1.0x
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.