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Home >> Isuzu >> 2000 >> Trooper S, 4WD, Part Time >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 3.2L & 3.5L >> Self-Diagnostic System >> Electric Throttle Control (Etc) System Check >> Diagnostic Procedure
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Diagnostic Procedure

  1. Perform On-Board Diagnostic II (OBD-II) System Check. See ON-BOARD DIAGNOSTIC II (OBD-II) SYSTEM CHECK in SELF-DIAGNOSTICS - INTRODUCTION article. After performing OBD-II system check, go to next step.
  2. Check for throttle body tampering, restricted or collapsed air intake duct, plugged 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. Repair any problems found 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. Check for smooth accelerator pedal, and ensure that pedal arm does not have excessive free play. Repair any problems found as necessary. If no problems were found, go to next step.
  4. Check for loose or poor connections at throttle body harness or acceleration position sensor (APS) harness connectors. Repair any problems found as necessary. Retest system. If no problems were found, go to next step.
  5. Use DVOM to check for open, short circuit to ground or voltage, or high resistance in throttle valve DC motor electrical circuit between DC motor and PCM. Check resistance of DC motor. DC motor resistance should be between 0.3-100 ohms. If faulty circuit or high resistance in DC motor exists, repair or replace as necessary. Retest system. If no problems were found, go to next step.
    NOTE: Varying APS sensor values are checked by depressing gas pedal.
  6. Turn ignition on, engine off. Using scan tool, check values for all TPS and acceleration position sensors (APS). At idle, APS1 should be 11-13 percent, APS2 and APS3 should be 87-88 percent, TPS1 should be 8-13 percent, and TPS2 should be 87-89 percent. At WOT, APS1 should be 85-89 percent, APS2 should be 11-15 percent, APS3 should be 32-36 percent, TPS1 should be 87-89 percent, and TPS2 should be 8-13 percent. Ensure that all sensor resistance values change smoothly as throttle position goes from closed to WOT. If any problems were found with any TPS readings, go to next step. If any problems were found with any APS readings, go to step  9. If no problems were found, go to step  11.
  7. Disconnect PCM connectors. Using DVOM, check for any opens, shorts to voltage, shorts to ground or poor connections by measuring at PCM harness connectors on TPS1 and TPS2 circuits. Resistance between 5-volt reference circuit and sensor ground circuit of TPS1 and TPS2 should be between 1-7 k/ohms. TPS1 and TPS2 have inverse resistance values. When measuring between sensor signal circuit and sensor ground circuit, at closed throttle, TPS1 has low resistance while TPS2 has high resistance. At WOT, resistance values are reversed. Ensure that both sensor resistance values change smoothly as throttle position goes from closed to WOT. If any test values were not as specified, go to next step. If no problems were found, go to step  8.
  8. Repair any opens, short to voltage, short to ground or poor connections found in any TPS electrical circuits. If wiring was okay, replace throttle valve assembly. Retest system.
    NOTE: Varying APS sensor values are checked by depressing gas pedal.
  9. Disconnect PCM connectors. Using DVOM, check for any opens, shorts to voltage, shorts to ground or poor connections by measuring at PCM harness connectors on APS1, APS2 and APS3 circuits. Resistance between 5-volt reference circuit and sensor ground circuit of APS1, APS2 and APS3 should be between 4-6 k/ohms. When measuring between sensor signal circuit and sensor ground circuit, ensure that sensor resistance values change smoothly as accelerator pedal goes from closed to WOT. If any test values were not as specified, go to next step.
  10. Repair any opens, short to voltage, short to ground or poor connections found in any APS electrical circuits. If wiring was okay, replace affected APS. Retest system.
  11. Replace and reprogram PCM. See PROGRAMMING .
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