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Home >> Chevrolet >> 1998 >> Corvette 2D Convertible, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine- Tests W/Codes >> Diagnostic Trouble Codes >> DTC P1518 - Pcm To TAC Module Serial Data Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Turn ignition on, engine off. Using test light connected to ground, probe both ends of THROT CONT fuse (located in underhood fuse block). If test light illuminates on at least one side of fuse, go to next step. If test light does not illuminate on either end of fuse, check ignition relay.
    NOTE: If DTC P0606 is also set, diagnose DTC P0606 first.
  3. Using scan tool, select SPECIAL FUNCTIONS option and PCM INTEGRITY STATUS. If scan tool indicates that PCM integrity status failed, go to step 28). If scan tool does not indicate that PCM integrity status failed, go to next step.
    NOTE: If Driver Information Center (DIC) is displaying REDUCED ENGINE POWER, go to step 5).
  4. Start engine and increase engine speed to 3000 RPM, if possible. Using scan tool, monitor FAIL THIS IGNITION option under DTC option. If this DTC fails this ignition cycle, go to next step. If this DTC does not fail this ignition cycle, see DIAGNOSTIC AIDS.
  5. Turn ignition off. Disconnect throttle actuator harness connector. Turn ignition on, engine off. Check voltage at both circuits of throttle actuator motor harness connector. If both circuits read greater than 8 volts, go to step 11). If both circuits do not read greater than 8 volts, go to next step.
  6. Turn ignition off. Check resistance on both throttle actuator motor harness connector circuits. If resistance is 0-5 ohms, go to step 9). If resistance is not 0-5 ohms, go to next step.
  7. Turn ignition off. Remove THROT CONT fuse. Check continuity from TAC side of fuse terminal to battery ground. If continuity is present, go to next step. If continuity is not present, go to step 10).
  8. Disconnect TAC module harness connector. Check continuity from TAC side of fuse terminal to battery ground. If continuity is present, go to step 19). If continuity is not present, go to step 27).
  9. Disconnect TAC module harness connector. Check continuity from throttle actuator motor harness connector to battery ground. If continuity is present, go to step 20). If continuity is not present, go to step 27).
  10. Turn ignition off. Disconnect TAC harness connector. Check continuity between TAC side of fuse terminal to ignition feed circuit of TAC at harness connector. If continuity is present, go to step 27). If continuity is not present, go to step 21).
  11. Turn ignition off. Disconnect TAC module harness connector. Turn ignition on, engine off. Check voltage at both circuits of throttle actuator motor harness connector. If both circuits read zero volts, go to next step. If both circuits do not read zero volts, go to step 22).
  12. Check continuity from TAC module ground circuit to battery ground. If continuity is present, go to next step. If continuity is not present, go to step 23).
  13. Check voltage between ground and both serial data circuits in TAC module harness connector. If both serial data circuits read 0-4.5 volts, go to next step. If both serial data circuits do not read 0-4.5 volts, go to step 16).
  14. Turn ignition off. Check resistance from serial data circuits at TAC module harness connector to battery ground. If DVOM reads OL for both circuits, go to step 17). If DVOM does not read OL for both circuits, go to next step.
  15. Disconnect PCM harness connector. Check resistance from serial data circuits at TAC module harness connector to battery ground. If resistance is 0-5 ohms, go to step 24). If resistance is not 0-5 ohms, go to step 28).
  16. Disconnect PCM harness connector. Check voltage at both serial data circuits at TAC module harness connector. If voltage is indicated on either circuits, go to step 25). If voltage is not indicated on either circuits, go to step 28).
  17. Disconnect PCM harness connector. Check continuity of each serial data circuit between TAC module harness connector to PCM harness connector. If continuity is present on both circuits, go to next step. If continuity is not present on both circuits, go to step 26).
  18. Reconnect PCM. Turn ignition on, engine off. Check voltage at serial data circuit at TAC module harness connector. If voltage reading is zero volts, go to step 28). If voltage reading is not zero volts, go to step 27).
  19. Repair TAC module ignition feed circuit for short to ground. After repairs, go to step 29).
  20. Repair throttle actuator motor circuit for short to ground. After repairs, go to step 29).
  21. Repair TAC module ignition feed circuit for an open in circuit. After repairs, go to step 29).
  22. Repair throttle actuator motor circuits for short to voltage. After repairs, go to step 29).
  23. Repair TAC module ground for open. After repairs, go to step 29).
  24. Repair serial data circuit for short to ground. After repairs are complete, go to step 29).
  25. Repair serial data circuit for short to voltage. After repairs are complete, go to step 29).
  26. Repair serial data circuit for an open. After repairs, go to step 29).
  27. Replace TAC module. After replacing module, go to step 29).
  28. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  29. 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 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).
  30. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs.
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