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Home >> GMC >> 1997 >> Forward Control 4.3 W, L35, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 60 (Engine Controls - Tests W/Codes - 5.7L (G Series)) >> Diagnostic Trouble Codes >> DTC P0121 - TP Sensor System Performance >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1997 GMC Savana Special, 1997 GMC Savana Camper Special, 1997 GMC Savana, 1997 Chevrolet RV Cutaway, and 1997 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the F - BASIC TESTING - 5.7L article. After performing OBD system check, go to next step.
  2. Install scan tool. Turn ignition on, with engine off. Using scan tool, observe TP sensor value. If TP sensor value is greater than 2 percent, go to step 4). If TP sensor value is not greater than 2 percent, go to next step.
  3. Depress throttle while observing scan tool. Throttle value should increase from about zero percent to 99.6 percent. Release throttle. Throttle value should drop to about 2 percent. If TP sensor value is greater than 2 percent, go to next step. If TP sensor value is not greater than 2 percent, go to step 5).
  4. Disconnect TP sensor connector. Using scan tool, monitor TP sensor. If TP sensor voltage is about zero volts, go to step 6). If TP sensor voltage is not about zero volts, go to step 9).
  5. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
  6. Check for poor connection at TP sensor. If a problem was found, go to next step. If a problem was not found, go to step 8).
  7. Repair as necessary. After repairs, go to step 10).
  8. Replace TP sensor. After replacing sensor, go to step 10).
  9. Replace VCM. After replacing VCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0121. Operate vehicle within the conditions for setting this DTC. If scan tool indicates this test ran and passed, go to next step. If scan tool does not indicate this test ran and passed, repeat step 2).
  11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test.
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