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Home >> Geo >> 1993 >> Prizm Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> (VIN 8) CODE CHARTS (PRIZM LSi) >> Code 42, Vehicle Speed Sensor CKT, Open Or Shorted CKT >> Notes

Code 42, Vehicle Speed Sensor CKT, Open Or Shorted CKT: Notes

Vehicle Speed Sensor (VSS) is an electronic relay mounted on transaxle. As transaxle rotates VSS, VSS provides speedometer with a vehicle speed input (voltage pulses). This signal drives speedometer. Speedometer converts vehicle speed input into a more precise waveform and provides PCM, and cruise control module with a vehicle speed input. PCM converts this input (ground pulses) into vehicle speed.

Code 42 will set if vehicle speed input is not sensed at PCM with engine speed 3000-5000 RPM and transaxle in gear, for at least 8 seconds.

NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. Determines if VSS is functioning properly.
  2. Checks for open in power feed to VSS.
  3. Checks for open or short in PCM speed input circuit or a faulty PCM.
  4. Determines if PCM or speedometer is faulty.
  5. Checks for open in ground to VSS.
  6. Checks for open in power feed to speedometer.
  7. Determines if VSS or speedometer is faulty.