LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Isuzu >> 1999 >> Trooper Part Time >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Trouble Code Identification >> DTC P0502: Vehicle Speed Sensor (VSS) Circuit/Low Input
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0502: Vehicle Speed Sensor (VSS) Circuit/Low Input

  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 (Black wire on 3.2L, or Black/Red wire on 3.5L). 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 (Black wire on 3.2L, or Black/Red wire on 3.5L) and voltage supply (Yellow wire on 3.2L, or Blue/Yellow wire on 3.5L). 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 (Black wire on 3.2L, or Black/Red wire on 3.5L) and speedometer wire (Blue/Black wire on 3.2L, or Light Green/White wire on 3.5L). 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 (Green connector on 3.2L, or Black connector on 3.5L), located behind left headlight assembly. Connect jumper wire between battery voltage and transmission side of 16-pin connector Yellow wire on 3.2L and Blue/Yellow wire on 3.5L. On 3.2L, 16-pin connector has 2 Yellow wires, the correct wire is in corner position of connector. On all models, using DVOM, measure voltage between ground and 16-pin connector Blue/Black wire on 3.2L and Light Green/White wire on 3.5L. On 3.2L, connect jumper wire between VSS ground at transmission side of 16-pin connector Black wire and ground. On 3.5L, disconnect Blue connector located next to 16-pin connector. Connect jumper wire between VSS ground at Blue connector Black/Red wire and ground. On all models, 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 PCM. Retest system.
scientia non olet · About LEMON Manuals