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.
1987 Honda Prelude Si, StandardFACTORY OEM SERVICE PROCEDURE
Auto. Trans.
- Raise and support front of vehicle. Set parking brake and block rear wheels. Insert voltmeter or test light positive probe into Yellow/Black wire terminal at control unit connector.
- Connect negative probe to ground. Start engine and place vehicle gear selector in "2" position and accelerate slowly. Battery voltage should be as indicated in SPEED SENSOR VOLTAGE CHECK table.SPEED SENSOR VOLTAGE CHECK
Speed Voltage Below 11 MPH Yes Above 16 MPH No - If voltmeter readings do not correspond to above MPH ranges, install new speed sensor and retest. If there was no voltage during step 2), check for bad electrical connection, fuse or faulty speed sensor. Repair or replace as necessary and retest.
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.
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