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 - C & K Series Except W/4L80-E Transmission: Notes
The ECM applies and monitors 12 volts on circuit No. 437. Circuit No. 437 is connected to the Digital Ratio Adapter Controller (DRAC) which alternately grounds this circuit when it is receiving voltage pulses from the Vehicle Speed Sensor (VSS). Scan tester reading should closely match speedometer reading.
- Code 24 will set if voltage on circuit No. 437 is constant, engine speed is greater than 1200 RPM, vehicle speed is less than 2 MPH vehicle is not in Park or Neutral and all conditions have been met for at least 10 seconds. These conditions are met during a road load deceleration.
- This test monitors DRAC voltage on circuit No. 437. With wheels turning, pulsing voltage should be present. Voltage variation will be greater at a low speed to an average of 4-6 volts at about 20 MPH.
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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.