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 a B+ signal to Vehicle Speed Sensor (VSS). While vehicle is moving, a reed switch inside VSS will open and close, toggling B+ signal high and low. ECM then converts this toggled high/low voltage into a vehicle speed that is displayed as MPH/KPH.
Code 24 will set if a constant voltage signal (high or low) is not detected at ECM for at least 4 seconds, with engine running and vehicle moving.
- Checks to see if problem is intermittent.
- If VSS is not receiving the 12 volts from the ECM, Code 24 will set. This step checks for an open in the Yellow/Green wire or for a faulty ECM.
- This checks for a poor ground connection, an open in the Black/Blue wire or for a faulty VSS.
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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.