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 (VSS)
The ECM applies and monitors 12 volts on circuit 437. Circuit 437 connects to the vehicle speed sensor which alternately grounds circuit 437 when the drive wheels are turning. This pulsing action takes place about 2000 times per mile and the ECM calculates vehicle speed based on the time between pulses.
- This test monitors the ECM voltage on circuit 437. with the wheels turning, the pulsing action varies the voltage. This variation is greater at low speeds to an average of 4-6 volts at about 20 mph (32 km/h).
- This test checks for a grounded circuit. A voltage of less than 1 volt indicates that circuit 437 is shorted to ground. Disconnect circuit 437 at the VSS, the VSS is faulty if the voltage now reads above 10 volts. If the voltage remains less than 10 volts, then circuit 437 wire is grounded. If the wire is not grounded, check for a faulty ECM connector or ECM.
- A steady 8-12 volts at the ECM connector indicates circuit 437 is open or a faulty VSS.
- Normal voltage is 1-6 volts and varying. This may indicate an intermittent problem if code 24 is shown.
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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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