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 (Pm Generator): Notes
The Permanent Magnet (PM) generator mounted in the transmission, produces a pulsing voltage signal whenever the vehicle speed is greater than 3 MPH. The voltage level and the number of pulses increase with vehicle speed. The ECM converts the pulsing voltage to MPH, which is used by the ECM in calculations to determine vehicle adjustments.
- Code 24 will set if vehicle speed equals zero MPH when transmission is not in Park or Neutral, engine speed is between 1600-4400 RPM, TPS indicates closed throttle, and a low airflow condition is sensed. All of these conditions must be met for at least 5 seconds.
- Before replacing the ECM, MEM-CAL should be checked for correct application.
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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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