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.
1992 Geo Prizm GSi, AutomaticFACTORY OEM SERVICE PROCEDURE
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.
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- If speedometer is inoperative, it could be the cause of Code 42.
- Checks to see if the VSS, located on back of instrument panel, will toggle 12 volts supplied by ECM.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.