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Home >> Nissan-Datsun >> 2004 >> Sentra SE-R >> Repair and Diagnosis >> External Pages >> Different car >> Section 12 (Engine Controls - Self-Diagnostics) >> Self-Diagnostic System >> Electric Throttle Control System Check >> 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 . 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 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 WIRING DIAGRAMS article. Measure resistance between throttle valve motor pins No. 2 and 3. Throttle valve motor resistance should be between 0.3 and 100 ohms. If faulty circuit or high resistance in throttle valve motor 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. 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. See WIRING DIAGRAMS article. Measure resistance between APS pins as specified. See CHECKING ACCELERATOR POSITION SENSOR RESISTANCE  table. APS resistance should be 2.6-4 k/ohms. If faulty circuit or high resistance is found, repair or replace as necessary. If no problem is found, go to next step.
    CHECKING ACCELERATOR POSITION SENSOR RESISTANCE

    Accelerator Position Sensor No. Measure Between Pins
    1 No. 4 & 10
    2 No. 3 & 8
    3 No. 1 & 7
  7. Using scan tool, retrieve any DTC's. If DTCs P1120, P1220, P1221, P1171, P1273, P1275, P1280, P1285, P1514, P1515. P1516 or P1523 are stored. Perform appropriate test, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs were stored, go to next step.
  8. 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 next step. If no problem is found, system is okay and testing is complete.
    ACCELERATOR POSITION & THROTTLE POSITION SENSOR VALUES

    Sensor Specification
    Accelerator Position Sensor 1
    Closed Throttle 9-17%
    Wide Open Throttle 83-91%
    Accelerator Position Sensor 2
    Closed Throttle 83-91%
    Wide Open Throttle 9-17%
    Accelerator Position Sensor 3
    Closed Throttle 83-91%
    Wide Open Throttle 30-38%
    Throttle Position Sensor 1
    Closed Throttle 6-12%
    Wide Open Throttle 79-83%
    Throttle Position Sensor 2
    Closed Throttle 88-94%
    Wide Open Throttle 19-23%
  9. Replace suspect sensor. See ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. After repair, recheck suspect sensor values as tested in step  8. If problem still exists, go to next step.
  10. 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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