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Home >> Chevrolet >> 2003 >> Corvette Base, 2D Convertible, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P1518: TAC Module Serial Data Fault >> Diagnostic Procedures
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Diagnostic Procedures

  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn ignition ON, with engine OFF. Remove the cover from the underhood electrical center. With a test light connected to ground, test both sides of the THROT CONT fuse. Does the test light illuminate on at least 1 side of the fuse? If yes, go to next step. If no, diagnose ignition relay.
  3. Turn ignition OFF. With a test light connected to ground, test for voltage at the THROT CONT fuse. Does the test light illuminate? If yes, go to step  22. If no, go to next step.
  4. Connect a scan tool. Is DTC P0604 also set? If yes, see DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 & P1683: PCM MEMORY . If no, go to next step.
    5. NOTE: If the Driver Information Center is displaying Reduced Engine Power, go to next step.
  5. Start the engine. Increase the engine speed to 3000 RPM, if possible. Monitor the Diagnostic Trouble Code (DTC) Info option using the scan tool. Does the scan tool indicate this DTC failed this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  6. Turn ignition OFF. Disconnect the throttle actuator motor harness connector. Turn ignition ON, with engine OFF. Test for voltage at both throttle actuator motor control circuits. Is voltage on both circuits above 8 V? If yes, go to step  12. If no, go to next step.
  7. Turn ignition OFF. Test both throttle actuator motor control circuits for continuity to ground. Is there continuity to ground? If yes, go to step  10. If no, go to next step.
  8. Turn ignition OFF. Remove the THROT CONT fuse. Test the TAC side of the fuse terminal for continuity to ground. Is there continuity to ground? If yes, go to next step. If no, go to step  11.
  9. Disconnect the TAC module 16-way harness connector. Test the TAC side of the fuse terminal for a short to ground. Did you find and correct the condition? If yes, go to step  28. If no, go to step  24.
  10. Disconnect the TAC module 16-way harness connector. Test the throttle actuator motor control circuits for a short to ground at the TAC module 16-way harness connector. Did you find and correct the condition? If yes, go to step  28. If no, go to step  24.
  11. Turn ignition OFF. Disconnect the TAC module 16-way harness connector. Test the TAC module ignition feed circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  28. If no, go to step  24.
  12. Turn ignition OFF. Disconnect the TAC module 16-way connector. Turn ignition ON, with engine OFF. Test for a short to voltage at both throttle actuator motor control circuits. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  13. Turn ignition OFF. Disconnect the TAC module 10-way harness connector. Test for a short between each throttle actuator motor control circuit and all other TAC module circuits. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  14. Test for an open or high resistance in the TAC module ground circuit. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  15. Test for voltage on the serial data circuits at the TAC module 16-way harness connector. Is voltage is 0-4.5 V for both circuits? If yes, go to next step. If no, go to step  18.
  16. Turn ignition OFF. Test both serial data circuits at the TAC module 16-way harness connector for continuity to ground. Does the DVOM indicate OL for both circuits? If yes, go to step  20. If no, go to next step.
  17. Disconnect the PCM connector containing the TAC module serial data circuits. Test both serial data circuits at the TAC module 16-way connector for a short to ground. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  18. Test for a short between both serial data circuits and all other circuits at the PCM and TAC module harness connectors. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  19. Test for a short to voltage on both serial data circuits at the TAC module 16-way connector. Did you find and correct the condition? If yes, go to step  28. If no, go to step  25.
  20. Disconnect the PCM connector that contains the TAC module serial data circuits. Test each serial data circuit between the TAC module 16-way harness connector and the PCM harness connector for an open or high resistance. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  21. Reconnect the PCM. Turn ignition ON. Test for voltage on the serial data circuit at the TAC module 16-way harness connector. Is voltage at 0 V? If yes, go to step  25. If no, go to step  24.
  22. Turn OFF the ignition Disconnect the 16-way TAC module harness connector. Test the TAC module ignition feed circuit for a short to battery voltage. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  23. Turn ignition ON. Test both TAC motor circuits for a short to voltage. Did you find and correct the condition? If yes, go to step  28. If no, go to next step.
  24. Test for an intermittent and/or poor connections at the TAC module harness connector. Did you find and correct the condition? If yes, go to step  28. If no, go to step  26.
  25. Test for an intermittent and/or poor connections at the PCM harness connector. Did you find and correct the condition? If yes, go to step  28. If no, go to step  27.
  26. Replace the TAC module. See THROTTLE ACTUATOR CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - CORVETTE article. Did you complete the replacement? If yes, go to next step. Did you complete the replacement? If yes, go to step  28.
  27. Replace the PCM. See REMOVAL & INSTALLATION - CORVETTE article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. Did you complete the replacement? If yes, go to next step.
  28. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  29. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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