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Home >> Chevrolet >> 2001 >> Camaro Base, 2D Convertible, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 7 (Engine Control System Self-Diagnostics - 5.7L) >> Diagnostic Tests >> DTC P1221: Throttle Position (TP) Sensors No. 1 & 2 Performance ("Y" Body) >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2000 Pontiac Firebird, 2000 Chevrolet Corvette, and 2000 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
    NOTE: If DTC P1120, P1220, P1515, P1516 and P1518 are also set, diagnose affected DTC(s) first.
  2. Turn ignition on, with engine off. Using scan tool, monitor TP SENSORS DISAGREE parameters. If scan tool indicates NO, go to next step. If scan tool does not indicate NO, go to step  5.
    NOTE: Disconnecting throttle actuator motor will cause additional DTCs to set.
  3. Remove duct from throttle body assembly. Disconnect throttle actuator motor connector. Manually open throttle blade to wide open throttle and then slowly return it to closed throttle while stopping briefly at 25, 50, 75 and 100 percent in each direction. If scan tool display changes from NO to YES, go to step  25. If scan tool display does not change from NO to YES, go to next step.
  4. Reconnect throttle actuator motor connector. Turn ignition off for 15 seconds. Turn ignition on, with engine off. Using scan tool, select DTC function, then enter this DTC. Monitor scan tool while moving wiring harness and related connectors. If scan tool indicates this test failed this ignition, go to step  14. If scan tool does not indicate that this test failed this ignition, go to DIAGNOSTIC AIDS .
  5. Disconnect throttle actuator harness connector. Turn ignition on, with engine off. Close throttle blade completely by hand while observing TP sensor No. 1 voltage on scan tool. If voltage reading is 0.13-0.67 volt, go to step  9. If voltage reading is not 0.13-0.67 volt, go to next step.
  6. Disconnect TP sensor harness connector. Using a jumper wire, jumper TP sensor No. 1 5-volt reference circuit to TP sensor No. 2 signal circuit. Observe TP sensor No. 2 voltage on scan tool. If voltage reading is 5 volts, go to next step. If voltage reading is not 5 volts, go to step  12.
  7. Jumper TP sensor No. 1 signal circuit to TP sensor No. 1 ground circuit. Monitor TP sensor No. 1 voltage on scan tool. If voltage reading is zero volts, go to step  24. If voltage reading is not zero volts, go to next step.
  8. Jumper TP sensor No. 1 signal circuit to battery ground circuit. Monitor TP sensor No. 1 voltage on scan tool. If voltage reading is zero volts, go to step  16. If voltage reading is not zero volts, go to step  14.
  9. Disconnect TP sensor harness connector. Jumper TP sensor No. 2 5-volt reference circuit to TP sensor No. 2 signal circuit. Monitor TP sensor No. 2 voltage on scan tool. If voltage reading is 5 volts, go to step  11. If voltage reading is not 5 volts, go to next step.
  10. Jumper TP sensor No. 2 signal circuit to TP sensor No. 1 5-volt reference circuit. Monitor TP sensor No. 2 voltage on scan tool. If voltage reading is 5 volts, go to step  18. If voltage reading is not 5 volts, go to step  20.
  11. Jumper TP sensor No. 1 signal circuit to TP sensor No. 2 ground circuit. Monitor TP sensor No. 1 voltage on scan tool. If voltage reading is zero volts, go to step  24. If voltage reading is not zero volts, go to step  22.
  12. Disconnect TAC module harness connector. Check resistance between TP sensor 5-volt reference circuit and TAC module. If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step  27.
  13. Check continuity between TP sensor No. 1 5-volt reference circuit and all other circuits in both TAC module connectors. If continuity exists, go to step  26. If continuity does not exist, go to step  28.
  14. Disconnect TAC module harness connectors. Check resistance between TP sensor No. 1 signal circuit and TAC module connector. If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step  27.
  15. Check continuity between TP sensor No. 1 signal circuit and all other circuit in both TAC connectors. If continuity exists, go to step  26. If continuity does not exist, go to step  28.
  16. Disconnect TAC module harness connectors. Check resistance between TP sensor No. 1 ground circuit and TAC module connector. If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step  27.
  17. Check continuity between TP sensor No. 1 ground circuit and all other circuits in both TAC module connectors. If continuity exists, go to step  26. If continuity does not exist, go to step  28.
  18. Disconnect TAC module harness connectors. Check resistance between TP sensor 5-volt reference circuit and TAC module connector. If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step  27.
  19. Check continuity between TP sensor No. 2 5-volt reference circuit and all other circuits in both TAC module connectors. If continuity exists, go to step  26. If continuity does not exist, go to step  28.
  20. Disconnect TAC module harness connectors. Check resistance between TP sensor No. 2 signal circuit and TAC module connector. If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step  27.
  21. Check continuity between TP sensor No. 1 signal circuit and all other circuit in both TAC module connectors. If continuity exists, go to step  26. If continuity does not exist, go to step  28.
  22. Disconnect TAC module harness connectors. Check resistance between TP sensor No. 2 ground circuit and TAC module connector. If resistance is 0-2 ohms, go to next step. If resistance is not 0-2 ohms, go to step  27.
  23. Check continuity between TP sensor No. 2 ground circuit and all other circuits in both TAC module connectors. If continuity exists, go to step  26. If continuity does not exist, go to step  28.
  24. Check for poor connections or terminal tension at TP sensor connector. Repair as necessary. After repairs, go to step  30. If connections or terminal tension is okay, go to next step.
  25. Replace throttle body assembly. After replacing throttle body, go to step  30.
  26. Repair circuits that are shorted together. After repairs, go to step  30.
  27. Repair circuit with high resistance. After repairs, go to step  30.
  28. Check for poor connections or terminal tension at TAC module connector. Repair as necessary. After repairs, go to step  30. If connections or terminal tension is okay, go to next step.
  29. Replace TAC module. After replacing module, go to next step.
  30. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions that set this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step  2.
  31. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs.
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