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Home >> Mitsubishi >> 2003 >> Lancer Evolution >> Repair and Diagnosis >> External Pages >> Different car >> Section 5 (Engine Controls - Self-Diagnostics) >> Diagnostic Tests >> DTC P0502: Vehicle Speed Sensor Circuit - Low Input >> Diagnostic Procedure
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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Isuzu Trooper. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD-II system check, go to next step.
  2. Observe speedometer while test driving vehicle. If speedometer works, go to step  10. If speedometer does not work, go to next step.
  3. Turn ignition off. Disconnect Vehicle Speed Sensor (VSS) 3-pin harness connector. VSS is located in tail shaft housing of transmission. Turn ignition on. Using test light connected to battery voltage, probe VSS harness connector terminal No. 2 (Black/Red wire). See Fig 1. If test light illuminates, leave harness connector disconnected and go to step  5. If test light does not illuminate, go to next step.
  4. Repair open in Black/Red wire between ground point C-39 and VSS. See WIRING DIAGRAMS article. Ground point is located at right rear corner of engine compartment, on fender well. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  5. Turn ignition on. Using DVOM, measure voltage between VSS harness connector terminals No. 1 (Blue/Yellow wire) and No. 2 (Black/Red wire). See Fig 1. If battery voltage exists, leave harness connector disconnected and go to step  7. If battery voltage does not exist, go to next step.
  6. Repair open or short to ground in Blue/Yellow wire between C-10 METER GAUGE fuse and VSS. See WIRING DIAGRAMS article. After repair ensure fuse is not blown. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  7. Turn ignition on. Using DVOM, measure voltage between VSS harness connector terminals No. 2 (Black/Red wire) and No. 3 (Light Green/White wire). Voltage reading should be 7.5-8.0 volts. If voltage is as specified, go to step  9. If voltage is not as specified, go to next step.
  8. Check for and repair open or short in Light Green/White wire between speedometer and VSS. See WIRING DIAGRAMS article. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  9. Replace speedometer. See INSTRUMENT PANELS - TROOPER article in ACCESSORIES & EQUIPMENT. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  10. Turn ignition off. Disconnect MAF sensor 3-pin harness connector. Remove air cleaner assembly. Disconnect Blue 16-pin in-line harness connector H-10. Harness connector is located behind left headlight assembly. Connect fused jumper wire between battery voltage and Blue 16-pin in-line harness connector H-10 terminal No. 9 (Blue/Yellow wire) on transmission side of in-line harness connector. See Fig 2. Connect jumper wire between ground and in-line harness connector H-10 terminal No. 4 (Black/Red wire) on transmission side of in-line harness connector. Connect jumper wire between positive side of DVOM and in-line harness connector H-10 terminal No. 11 (Light Green/White wire) on transmission side of in-line harness connector. Connect negative side of DVOM to ground. Raise and support rear of vehicle. Place transmission in Neutral. Turn ignition on. Observe DVOM readings, while rotating rear wheels by hand. Voltage reading should toggle back and forth between .6-10.0 volts. If voltage toggles as specified, go to step next step. If voltage does not toggle as specified, go to step  12.
  11. Replace VSS. See REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
  12. Check for and repair open or short between PCM harness connector and speedometer harness connector. See WIRING DIAGRAMS article. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem with wiring is found, go to next step.
  13. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE REPLACEMENT  under POWERTRAIN CONTROL MODULE. Use scan tool to clear DTC and verify repair.
Fig 1: Identifying Vehicle Speed Sensor Harness Connector Terminals
G00077232Courtesy of ISUZU MOTOR CO.
Fig 2: Identifying In-Line Harness Connector H-10 Terminals
G00077233Courtesy of ISUZU MOTOR CO.
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