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.
1993 Geo Prizm Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Solenoid Test
- Turn ignition to LOCK position. Install TECH-1 scan tester. Turn ignition on, engine off. Select left front or right front. Release motor on channel being tested. Select solenoid for the same channel.
- With no brake pressure applied, turn solenoid on. Depress brake pedal. Pedal should be very high and firm. If pedal sinks to the floor, solenoid is leaking and not closing or check ball is leaking.
- With brake pressure still applied, turn solenoid off. Brake pedal should immediately drop. If brake pedal rises or slowly sinks to the floor, go to step 5). If brake pedal does not drop and motor is moving, solenoid is stuck in on or off position. To verify solenoid position, go to next step.
- With brake still applied, apply the motor to the channel being tested. If pedal rises, solenoid is stuck open (off) or check ball is leaking. If pedal drops suddenly, solenoid is stuck closed (on).
- Switch the 2 solenoid connectors. Repeat test to channel in question. If pedal slowly sinks to the floor, check valve is leaking. Replace hydraulic modulator. If test now works properly, test the opposite channel. If brake pedal sinks or rises, replace solenoid.
Factory Service Tools
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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.