Diagnostic Procedure
- Perform ON-BOARD DIAGNOSTIC II SYSTEM CHECK . After performing OBD-II system check, go to next step.
- 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.
- 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.
- Check for loose or poor connections at throttle valve assembly or Acceleration Position (AP) sensor 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.
- 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 ECM. See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. See THROTTLE POSITION SENSOR RESISTANCE table. 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.
- Use DVOM to check for open, short to ground, short to voltage, or high resistance in circuits between Acceleration Position Sensor 1 (APS1), Acceleration Position Sensor 2 (APS2), and Acceleration Position Sensor 3 (APS3). See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. See ACCELERATION POSITION SENSOR RESISTANCE table. If short circuit or high resistance in acceleration sensor 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.
- If DTC P1120, P1220, P1221, P1271, P1272, P1273, P1275, P1280, P1285, P1514, P1515, P1516, or P1523 are stored, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are store, go to next step.
- 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, go to step 10
.ACCELERATOR POSITION & THROTTLE POSITION SENSOR VALUES
Sensor Specification - % Accelerator Position Sensor 1 Closed Throttle 9-17 Wide Open Throttle 81-93 Accelerator Position Sensor 2 Closed Throttle 81-93 Wide Open Throttle 9-17 Accelerator Position Sensor 3 Closed Throttle 81-93 Wide Open Throttle 28-40 Throttle Position Sensor 1 Closed Throttle 6-12 Wide Open Throttle 78-83 Throttle Position Sensor 2 Closed Throttle 88-94 Wide Open Throttle 19-23 - Replace faulty sensor. See SENSORS & SWITCHES in REMOVAL & INSTALLATION article. After repair, go to VERIFYING VEHICLE REPAIR under SELF-DIAGNOSTIC SYSTEM.
- Replace and reprogram ECM. See POWERTRAIN CONTROL MODULE REPLACEMENT under POWERTRAIN CONTROL MODULE. Use scan tool to clear DTC and verify repair.