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Home >> Isuzu >> 2000 >> Trooper S, 4WD, Part Time >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 3.2L & 3.5L >> Diagnostic Trouble Code Identification >> DTC P0502: Vehicle Speed Sensor (VSS) Circuit/Low Input >> Diagnostic Procedure
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Diagnostic Procedure

  1. Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. 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 test light to positive battery terminal. 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 circuit and voltage supply circuit. If battery voltage is not displayed on DVOM, go to next step. If battery voltage is displayed, go to step  7.
  6. Repair open or short to ground. After repair ensure meter fuse is not blown. Retest system.
  7. With sensor disconnected, turn ignition on. Using DVOM, measure voltage between VSS connector ground circuit and speedometer circuit. If DVOM reads 7.5-8.0 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.
  9. Replace speedometer. Retest system.
  10. Turn ignition off. Disconnect MAF sensor connector. Remove air cleaner assembly. Disconnect 16-pin connector located behind left headlight assembly. Connect jumper wire between battery voltage and transmission side of 16-pin connector Blue/Yellow wire. Measure voltage between ground and Black 16-pin connector Light Green/White wire. Disconnect Blue connector located next to Black 16-pin connector. Connect jumper wire between VSS ground at Blue connector Black/Red wire and ground. Raise and support rear of vehicle. Place transmission in Neutral. Rotating rear wheels by hand, observe DVOM readings. If reading toggles between .6 volt and 10 volts, go to step  12. If readings are not as specified, go to next step.
  11. Replace VSS. Retest system.
  12. Repair open or short between PCM and speedometer. Retest system. If problem was not found, go to next step.
  13. Replace and reprogram PCM. See PROGRAMMING . Retest system.
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