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Home >> Chevrolet >> 2000 >> Suburban C2500 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - Gasoline - 4.8L, 5.3L & 6.0L >> Diagnostic Tests >> DTC P1518: Throttle Actuator Control Module Serial Data Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC SYSTEM CHECK . After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using test light connected to ground, probe both sides of THROT CONT fuse, located in underhood fuse/relay block. If test light illuminates on at least one side of fuse, go to next step. If test light does not illuminate, diagnose ignition relay circuit.
  3. Turn ignition off. Using test light connected to ground, probe THROT CONT fuse. If test light illuminates, go to step  31. If test light does not illuminate, go to next step.
  4. Check if DTC P0606 is also set. If DTC P0606 is set, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC SYSTEM CHECK . If DTC P0606 is not set, go to next step.
    5. NOTE: Observe Driver Information Center (DIC) display. If DIC is displaying REDUCED ENGINE POWER, go to next step.
  5. Operate engine at idle. Increase engine speed to 3,000 RPM, if possible. Using scan tool, monitor DTC option. If this DTC failed this ignition, go to next step. If this DTC did not fail this ignition, see DIAGNOSTIC AIDS .
    6. NOTE: Disconnecting throttle actuator motor harness connector causes additional DTCs to set.
  6. Turn ignition off. Disconnect throttle actuator motor harness connector. Turn ignition on, with engine off. Using a DVOM, check voltage at both circuits of throttle actuator motor harness connector. If voltage reading on both circuits is greater than 8 volts, go to step  12. If voltage reading on both circuits is not greater than 8 volts, go to next step.
  7. Turn ignition off. Check resistance of throttle actuator motor circuits from harness connector to battery ground. If resistance is 0-5 ohms, go to step  10. If resistance is not 0-5 ohms, go to next step.
  8. Turn ignition off. Remove THROT CONT fuse. Check continuity from TAC side of fuse terminal to battery ground. If continuity exists, go to next step. If continuity does not exist, go to step  11.
  9. Disconnect TAC module 16-pin connector. Check continuity from TAC side of fuse terminal to battery ground. If continuity exists, go to step  22. If continuity does not exist, go to step  32.
  10. Disconnect TAC module 16-pin connector. Check continuity from throttle actuator motor harness connector to battery ground. If continuity exists, go to step  23. If continuity does not exist, go to step  32.
  11. Turn ignition off. Disconnect TAC module 16-pin connector. Check continuity between TAC side of fuse terminal to ignition feed circuit of TAC module harness connector. If continuity exists, go to step  32. If continuity does not exist, go to step  24.
  12. Turn ignition off. Disconnect TAC module 16-pin connector. Turn ignition on, with engine off. Check voltage at both circuits of throttle actuator motor harness connector. If voltage reading on both circuits is about zero volts, go to next step. If voltage reading on both circuits is not about zero volts, go to step  25.
  13. Turn ignition off. Disconnect TAC module 10-pin connector. Check continuity of both throttle actuator motor circuits to all other TAC module terminals. If continuity from either throttle actuator motor circuit to any other TAC module circuit exists, go to step  30. If continuity from either throttle actuator motor circuit to any other TAC module circuit does not exist, go to next step.
  14. Check continuity from TAC module ground circuit to battery ground. If continuity exists, go to next step. If continuity does not exist, go to step  26.
  15. Check voltage at serial data circuits at TAC module 16-pin harness connector. If voltage reading on both serial data circuit is 0-4.5 volts, go to next step. If voltage reading on both serial data circuit is not 0-4.5 volts, go to step  18.
  16. Turn ignition off. Check resistance from serial data circuits at TAC module 16-pin connector to battery ground. If DVOM displays OL on both circuits, go to step  20. If DVOM does not display OL on both circuits, go to next step.
  17. Disconnect PCM connector C1. Check resistance from serial data circuits at TAC module 16-pin connector to battery ground. If resistance is 0-5 ohms, go to step  27. If resistance is not 0-5 ohms, go to next step.
  18. Check continuity from both serial data circuits to all other circuits at PCM and TAC module connectors. If continuity exists from either serial data circuit to any other circuit, go to step  30. If continuity does not exist from either serial data circuit to any other circuit, go to next step.
  19. Check voltage of both serial data circuits at TAC module 16-pin connector. If voltage is indicated on either circuit, go to step  28. If voltage is not indicated on either circuit, go to step  33.
  20. Disconnect PCM connector C1. Check continuity of each serial data circuit between TAC module 16-pin connector to PCM harness connector. If continuity exists on both serial data circuits, go to next step. If continuity does not exist on both serial data circuits, go to step  29.
  21. Reconnect PCM harness connectors. Turn ignition on, with engine off. Check voltage at serial data circuit at TAC module 16-pin harness connector. If voltage reading is zero volts, go to step  33. If voltage reading is not zero volts, go to step  32.
  22. Repair TAC module ignition feed circuit for a short to ground. After repairs, go to step  34.
  23. Repair throttle actuator motor circuit for short to ground on affected circuit. After repairs, go to step  34.
  24. Repair open in TAC module ignition feed circuit. After repairs, go to step  34.
  25. Repair throttle actuator motor circuits for short to voltage on affected circuit. After repairs, go to step  34.
  26. Repair open in TAC module ground circuit. After repairs, go to step  34.
  27. Repair serial data circuit for short to ground on affected circuit. After repairs, go to step  34.
  28. Repair serial data circuit for short to voltage on affected circuit. After repairs, go to step  34.
  29. Repair serial data circuit for open on affected circuit. After repairs, go to step  34.
  30. Repair circuits that display continuity. After repairs, go to step  34.
  31. Repair ignition feed circuit for short to voltage. After repairs, go to step  34.
  32. Replace TAC module. After replacing module, go to step  34.
  33. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  34. 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.
  35. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs.
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