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Home >> Isuzu >> 1997 >> Rodeo LS, 2.6 E >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 2.6L >> Circuit Testing >> DTC P0502 - VSS Circuit Low Input >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
  2. Check speedometer. If speedometer works, go to step 10). If speedometer does not work, go to next step.
  3. Disconnect VSS harness connector and turn ignition on (with engine off). Connect a test light to positive battery post. Probe VSS connector ground terminal. If test light illuminates, go to step 5). If test light does not illuminate, go to next step.
  4. Repair sensor ground. Retest system.
  5. With sensor disconnected, turn ignition on. Using DVOM, probe VSS connectors ground and voltage supply. If battery voltage is displayed, go to step 7). If battery voltage is not displayed on DVOM, go to next step.
  6. Repair open or short to ground which may have blown meter fuse. Retest system.
  7. With sensor disconnected, turn ignition on. Using DVOM, probe VSS connectors ground and speedometer wire (Blue/Black wire). If DVOM reads 7.5-8 volts, go to step 9). If reading is not as specified, go to next step.
  8. Repair open or short circuit between speedometer and VSS. Retest system. If no open or short was found, go to next step.
  9. Replace speedometer. Retest system.
  10. Raise and support rear of vehicle. Reconnect VSS harness connector. Using DVOM backprobe terminal containing wire from speedometer and chassis ground. Turn ignition on, with engine off and place transmission in Neutral. Rotating rear wheels by hand, observe DVOM readings. If readings are not as specified, go to next step. If readings toggle between .6 volt and 10 volts, go to step 12).
  11. Replace VSS. Retest system.
  12. Check for open or short between PCM and speedometer, speedometer ground, faulty meter circuit board or faulty speedometer. Repair as necessary. Retest system. If no open or short was found, go to next step.
  13. Replace PCM. Program replacement PCM using required equipment. Retest system.
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