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 42, Vehicle Speed Sensor Circuit: Notes
ECM provides a 12-volt signal to the Vehicle Speed Sensor (VSS). The VSS will toggle the signal low and high, indicating vehicle is moving. Code 42 will set if signal line remains high or low for 4 seconds or more.
- If speedometer is inoperative, it could set Code 42.
- Checks to see if VSS behind instrument cluster will toggle the 12 volts supplied by ECM.
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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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