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.
1979 Honda Prelude Automatic TransFACTORY OEM SERVICE PROCEDURE
Speed Sensor Check
- Jack up front of vehicle and support with safety stands. Block rear wheels and set parking brake.
- Connect voltmeter positive probe to Yellow/Black wire terminal at emission control box connector. Connect negative probe to known good ground (Black ground wire). See Fig 1. Start engine.
- Select 2nd gear and accelerate engine slowly while observing voltmeter. Voltmeter should show battery voltage above 5-15 MPH (above 20 MPH on Accord and Prelude). With vehicle speed below 5 MPH (10 MPH on Accord and Prelude), voltmeter should show no voltage.
- If no voltage exists above specified MPH, check for bad electrical connections, blown fuse, or faulty speed sensor. Repair or replace as necessary. If voltage readings do not agree with specified MPH range, install new speedometer and speed sensor assembly and repeat test.
Factory Service Tools
Use the Manual With the Right Hardware
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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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