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.
Circuit Description
Vehicle speed is signaled to PCM by Vehicle Speed Sensor (VSS). Sensor is a Permanent Magnet (PM) generator mounted to transaxle case extension. PM generator produces an AC voltage as speed sensor rotor teeth pass sensor's magnetic field. PCM converts AC voltage into digital signal. PCM uses vehicle speed to determine shift timing, TCC apply and release, and gear ratio calculations. VSS voltage will vary from .5 volt AC at 100 RPM to more than 100 volts AC at 6000 RPM. VSS resistance value is 981-1864 ohms. DTC P0502 will set if PCM detects a low vehicle output speed when vehicle has high engine speed in drive gear.
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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.