Throttle Body: Non-Turbo
- Ensure throttle cable and throttle lever on throttle body moves smoothly. Note location of throttle control motor on throttle body. See Fig 1.
- Turn ignition on. Rotate throttle lever on throttle body to full throttle while listing for operating sound at throttle control motor and that no grinding noise is heard at throttle control motor and throttle body. Throttle lever will also rotate accelerator pedal position sensor.
- If throttle control motor operating sound is heard, go to next step. If throttle control motor operating sound is not heard, throttle control motor, wiring harness or Engine Control Module (ECM) may be defective. The ECM is located below passenger's side of instrument panel, underneath carpet on the floor. Go to step 11) for testing of throttle control motor.
- To test operation of Throttle Position (TP) sensor and accelerator pedal position sensor, connect scan tool to data link connector No. 3. See Figure. Scan tool is used to read throttle valve opening which is displayed as a percentage.
- Rotate throttle lever on throttle body to full throttle while reading throttle valve opening on scan tool which is accessed by THROTTLE POS under CURRENT DATA. Throttle valve opening should be at least 60 percent.
- If throttle valve opening is at least 60 percent, go to next step. If throttle valve opening is not at least 60 percent, problem may exist in TP sensor, accelerator pedal position sensor, wiring circuit or ECM. Go to steps 13) and 14) for testing of TP sensor and accelerator pedal position sensor.
- Start engine and allow engine to idle. Check operation of Malfunction Indicator Light (MIL) on instrument panel. If MIL is not illuminated, go to next step. If MIL is illuminated, a Diagnostic Trouble Code (DTC) may be stored in the ECM. For diagnosis of DTC, see appropriate TESTS W/CODES article.
- To test operation of air assist system, allow engine to warm to normal operating temperature. Apply parking brake. Place transmission in Neutral. Ensure A/C is off.
- Using scan tool, note engine idle speed with and A/C turned off, and then with A/C turned on. Engine idle speed should be 650-750 RPM with A/C turned off and 700-800 RPM with A/C turned on.
- With engine idling, pinch air assist hose closed and note engine idle speed. See Fig 2. Engine idle speed should decrease and then return to the original engine idle speed. If engine idle speed does not decrease and then return to normal idle speed, throttle body, wiring circuit or ECM may be defective.
- To test throttle control motor, disconnect electrical connector at throttle control motor and note terminal identification. See Fig 3.
- Using ohmmeter, check resistance between specified terminals. See THROTTLE CONTROL MOTOR RESISTANCE table. If resistance is within specification, reinstall electrical connector. If resistance is not within specification, replace throttle control motor. See appropriate REMOVE/INSTALL/OVERHAUL
article.THROTTLE CONTROL MOTOR RESISTANCE
Terminals Ohms @ 68°F (20°C) 1 (M+) & 2 (M-) .3-100.0 3 (CL-) & 4 (CL+) 4.2-5.2 - To test TP sensor, disconnect electrical connector at TP sensor. See Fig 1. Using ohmmeter, check resistance between terminals VC and E2 on TP sensor. See Fig 4. Replace TP sensor if resistance is not 1.2-3.2 ohms at 68°F (20°C). See appropriate REMOVE/INSTALL/OVERHAUL article.
- To test accelerator pedal position sensor, disconnect electrical connector at accelerator pedal position sensor. See Fig 1. Using ohmmeter, check resistance between terminals VC and E2 on accelerator pedal position sensor. See Fig 5. Replace accelerator pedal position sensor if resistance is not 1.2-3.2 ohms at 68°F (20°C). See appropriate REMOVE/INSTALL/OVERHAUL article.