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Home >> Isuzu >> 2002 >> Axiom Base, RWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 3.2L >> Self-Diagnostic System >> Electric Throttle Control System Check >> Diagnostic Procedure
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Diagnostic Procedure

  1. Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK . After performing OBD-II system check, go to next step.
  2. Check for throttle body tampering, restricted or collapsed air intake duct, restricted air filter or any foreign objects blocking air intake system. Check for any objects blocking throttle passage or throttle bore, excessive deposits in throttle passage or on throttle plate. Check for smooth movement of throttle lever. Throttle spring should not bind or have excessive play. Throttle lever should move with only 9 INCH lbs. (1.0 N.m) of force applied. Turn ignition on and ensure that throttle lever operation is smooth when accelerator pedal is depressed. If problem is found, repair as necessary. If no problems were found, go to next step.
  3. Check for accelerator pedal tampering or objects that may block free movement of pedal. Ensure accelerator pedal moves freely and smoothly, and ensure that pedal arm does not have excessive free play. If problem is found, repair as necessary. If no problems were found, go to next step.
  4. Check for loose or poor connections at throttle body or Accelerator Position Sensor (APS) harness connectors. If problem is found, repair or replace as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problems were found, go to next step.
  5. Use DVOM to check for open, short to ground, short to voltage, or high resistance in circuits between Throttle Position Sensor 1 (TPS1), Throttle Position Sensor 2 (TPS2), throttle valve motor and PCM. See instructions under TEST DESCRIPTION . See WIRING DIAGRAMS article. If short circuit or high resistance in throttle valve assembly is present, repair or replace as necessary. After repair is complete, see VERIFYING VEHICLE REPAIR  under SELF-DIAGNOSTIC SYSTEM. If no problems were found, go to next step.
  6. Start and run engine until coolant temperature is 176°F (80°C) or more. Turn ignition on, engine off. Using scan tool, check that all TPS and APS percentage parameters are as specified. See ACCELERATOR POSITION & THROTTLE POSITION SENSOR VALUES  table. Ensure that all sensor resistance values change smoothly as throttle position goes from closed to wide open throttle. If problem is found, go to step  10. If no problem is found, go to next step.
    ACCELERATOR POSITION & THROTTLE POSITION SENSOR VALUES

    Sensor Specification (%)
    Accelerator Position Sensor 1
    Closed Throttle 11-13
    Wide Open Throttle 85-89
    Accelerator Position Sensor 2
    Closed Throttle 87-88
    Wide Open Throttle 11-15
    Accelerator Position Sensor 3
    Closed Throttle 87-88
    Wide Open Throttle 32-36
    Throttle Position Sensor 1
    Closed Throttle 1-6
    Wide Open Throttle 98-100
    Throttle Position Sensor 2
    Closed Throttle 88-94
    Wide Open Throttle 19-23
  7. Replace throttle valve assembly. See ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step.
  8. Disconnect APS 10-pin harness connector. Check for open circuit, short to voltage and/or ground or poor connection in circuits between APS1, APS2, APS3 and PCM. Measure resistance between APS pins as specified. See instructions under TEST DESCRIPTION . 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.
  9. Replace APS. See ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. After repair, go to next step.
  10. Using scan tool, retrieve any DTCs. If DTCs P1125, P1290, P1295 or P1299 are stored. Perform appropriate test, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If none of these DTCs were stored, go to next step.
  11. Using scan tool, retrieve any DTCs. If DTCs P1514, P1515, P1516, P1523, P1271, P1272 or P1273 are stored. Perform appropriate test, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If none of these DTCs were stored, go to next step.
  12. Replace and reprogram PCM. See POWERTRAIN CONTROL MODULE REPLACEMENT  under POWERTRAIN CONTROL MODULE. Use scan tool to clear DTC and verify repair.
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