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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. Turn ignition off. Check BACK fuse (15-amp) and STOP LAMP fuse (15-amp). Both fuses are located in dash fuse box. If fuses are blown, replace as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If fuses are okay, go to next step.
  3. Check brake switch adjustment. For adjustment procedure, see ON-VEHICLE ADJUSTMENTS article. If problem is found, adjust as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  4. Check brake pedal for excessive movement, and smooth operation. If problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  5. Disconnect brake switch 4-pin harness connector. Brake switch is located on brake pedal. Using DVOM, measure resistance between specified brake switch terminals with brake pedal in rest position. See CHECKING BRAKE SWITCH  table. See Fig 1. If resistance is as specified, go to next step. If resistance is not as specified, go to step  9.
    CHECKING BRAKE SWITCH

    Measure Between Brake Switch Terminals Specification
    Brake Pedal At Rest
    1 & 4 No Continuity
    2 & 3 Continuity
    Brake Pedal Pressed
    1 & 4 Continuity
    2 & 3 No Continuity
  6. Measure resistance between specified brake switch terminals with brake pedal pressed. See CHECKING BRAKE SWITCH  table. See Fig 1. If resistance is as specified, go to next step. If resistance is not as specified, go to step  9.
  7. Check for open or short to ground in brake pedal switch circuits between brake switch and PCM or appropriate fuse. See WIRING DIAGRAMS article. If problem is found, repair as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problem is found, go to next step.
  8. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE REPLACEMENT  under POWERTRAIN CONTROL MODULE. Use scan tool to clear DTC and verify repair.
  9. Replace brake switch. See REMOVAL, OVERHAUL & INSTALLATION article. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM.
Fig 1: Identifying Brake Switch Terminals
G00077235Courtesy of ISUZU MOTOR CO.
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