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.
Code 24, Vehicle Speed Sensor Circuit: Notes
ECM supplies 12 volts to VSS. With vehicle moving, the reed switch inside the VSS will open and close 4 times per revolution of speedometer cable. As the reed switch opens and closes, voltage at the ECM is toggled high and low. ECM converts this toggled voltage into vehicle speed displayed as MPH or KPH. Code 24 will set if a constant voltage (high or low) lasts at least 4 seconds.
- Checks for intermittents.
- Checks for VSS not receiving 12 volts from ECM (open in Yellow/Green wire or faulty ECM).
- Checks for poor ground connection or a faulty VSS.
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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