LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Buick >> 1998 >> Century Custom >> Repair and Diagnosis >> Accessories & Equipment >> Cruise Control Systems >> Testing >> Cruise Control Is Inoperative
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Cruise Control Is Inoperative

NOTE: To avoid misdiagnosis, perform rev test and trouble shooting. See REV TEST  and TROUBLE SHOOTING. Check for stored DTCs. See appropriate TESTS W/CODES article in ENGINE PERFORMANCE section.
  1. Check STOP LAMPS fuse (15-amp) located in fuse block, in right front door opening. If fuse is blown, go to next step. If fuse is okay, go to step 3).
  2. Repair short to ground in Orange wire between fuse block and brake switch.
  3. Check CRUISE fuse (10-amp) located in fuse block, in right front door opening. If fuse is blown, go to next step. If fuse is okay, go to step 5).
  4. Repair short to ground in Brown wire between fuse block, multifunction lever (cruise control switch), cruise control module assembly and cruise control release switch.
  5. Disconnect cruise control module assembly connector. Turn ignition switch to RUN position. Using a test light connected to ground, probe cruise control module assembly connector (harness side) terminal "F" (Brown wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 17).
  6. Using a test light, probe between cruise control module assembly connector (harness side) terminals "F" (Brown wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 18).
  7. Turn cruise control switch to ON position. Using a test light, probe between cruise control module assembly connector (harness side) terminals "A" (Gray wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 19).
  8. Press and hold cruise control switch in SET position. Using a test light, probe between cruise control module assembly connector (harness side) terminals "B" (Dark Blue wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 26).
  9. Press and hold cruise control switch in R/A position. Using a test light, probe between cruise control module assembly connector (harness side) terminals "C" (Gray/Black wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 30).
  10. Using a test light, probe between cruise control module assembly connector (harness side) terminals "D" (Brown wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 34).
  11. Using a test light, probe between cruise control module assembly connector (harness side) terminals "G" (White wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 47).
  12. Using a test light, probe between cruise control module assembly connector (harness side) terminals "B" (Dark Blue wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 50).
  13. Check for a short to voltage in Dark Blue wire between multifunction lever (cruise control switch) and cruise control module assembly. If Dark Blue wire is faulty, go to next step. If Dark Blue wire is okay, go to step 25).
  14. Repair short to voltage in Dark Blue wire between multifunction lever (cruise control switch) and cruise control module assembly.
  15. Check for a short to voltage in Gray/Black wire between multifunction lever (cruise control switch) and cruise control module assembly. If Gray/Black wire is faulty, go to next step. If Gray/Black wire is okay, go to step 25).
  16. Repair short to voltage in Gray/Black wire between multifunction lever (cruise control switch) and cruise control module assembly.
  17. Repair poor connection or open in Brown wire between fuse block, multifunction lever (cruise control switch), cruise control module assembly and cruise control release switch.
  18. Repair poor connection or open in Black wire between cruise control module assembly and ground connection.
  19. Check for a poor connection or open in Brown wire between fuse block and multifunction lever (cruise control switch). If Brown or Pink wire is faulty, go to next step. If Brown wire is okay, go to step 21).
  20. Repair poor connection or open in Brown wire between fuse block and multifunction lever (cruise control switch).
  21. Check for a short to ground in Gray wire between multifunction lever (cruise control switch) and cruise control module assembly. If Gray wire is faulty, go to next step. If Gray wire is okay, go to step 23).
  22. Repair short to ground in Gray wire between multifunction lever (cruise control switch) and cruise control module assembly.
  23. Check for a poor connection or open in Gray wire between multifunction lever (cruise control switch) and cruise control module assembly. If Gray wire is faulty, go to next step. If Gray wire is okay, go to step 25).
  24. Repair poor connection or open in Gray wire between multifunction lever (cruise control switch) and cruise control module assembly.
  25. Replace multifunction lever (cruise control switch). See STEERING COLUMN SWITCHES article.
  26. Check for a short to ground in Dark Blue wire between multifunction lever (cruise control switch) and cruise control module assembly. If Dark Blue wire is faulty, go to next step. If Dark Blue wire is okay, go to step 28).
  27. Repair short to ground in Dark Blue wire between multifunction lever (cruise control switch) and cruise control module assembly.
  28. Check for a poor connection or open in Dark Blue wire between multifunction lever (cruise control switch) and cruise control module assembly. If Dark Blue wire is faulty, go to next step. If Dark Blue wire is okay, go to step 25).
  29. Repair poor connection or open in Dark Blue wire between multifunction lever (cruise control switch) and cruise control module assembly.
  30. Check for a short to ground in Gray/Black wire between multifunction lever (cruise control switch) and cruise control module assembly. If Gray/Black wire is faulty, go to next step. If Gray/Black wire is okay, go to step 32).
  31. Repair short to ground in Gray/Black wire between multifunction lever (cruise control switch) and cruise control module assembly.
  32. Check for a poor connection or open in Gray/Black wire between multifunction lever (cruise control switch) and cruise control module assembly. If Gray/Black wire is faulty, go to next step. If Gray/Black wire is okay, go to step 25).
  33. Repair poor connection or open in Gray/Black wire between multifunction lever (cruise control switch) and cruise control module assembly.
  34. Turn ignition switch to OFF position. Disconnect cruise control release switch connector. Turn ignition switch to ON position. Using a test light, probe between cruise control release switch connector (harness side) terminal "B" (Brown wire) and cruise control module assembly connector (harness side) terminal "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 36).
  35. Connect a jumper wire between cruise control release switch connector (harness side) terminals. Using a test light, probe between cruise control module assembly connector (harness side) terminals "D" (Brown wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to step 40). If test light does not illuminate, go to step 44).
  36. Check for a short to ground in Brown wire on between fuse block and cruise control release switch. If Brown wire is faulty, go to next step. If Brown wire is okay, go to step 38).
  37. Repair short to ground in Brown wire between fuse block and cruise control release switch.
  38. Check for a poor connection or open in Brown wire between fuse block and cruise control release switch. If Brown wire is faulty, go to next step. If Brown wire is okay, go to step 42).
  39. Repair poor connection or open in Brown wire between fuse block and cruise control release switch.
  40. Check for a short to ground in Brown wire between cruise control release switch and cruise control module assembly. If Brown wire is faulty, go to next step. If Brown wire is okay, go to step 42).
  41. Repair short to ground in Brown wire between cruise control release switch and cruise control module assembly.
  42. Check for a poor connection or open in Brown wire between cruise control release switch and cruise control module assembly. If Brown wire is faulty, go to next step. If Brown wire is okay, go to step 44).
  43. Repair poor connection or open in Brown wire between cruise control release switch and cruise control module assembly.
  44. Check cruise control release switch for proper adjustment. See CRUISE CONTROL RELEASE SWITCH & BRAKE SWITCH ADJUSTMENT  . If cruise control release switch is properly adjusted, go to next step. If cruise control release switch is not properly adjusted, go to step 46).
  45. Replace cruise control release switch. See CRUISE CONTROL RELEASE SWITCH & BRAKE SWITCH  .
  46. Adjust cruise control release switch. See CRUISE CONTROL RELEASE SWITCH & BRAKE SWITCH  .
  47. Check brake switch for proper adjustment. See procedures in CRUISE CONTROL RELEASE SWITCH & BRAKE SWITCH ADJUSTMENT  . If brake switch is properly adjusted, go to next step. If brake switch is not properly adjusted, go to step 49).
  48. Replace brake switch. See CRUISE CONTROL RELEASE SWITCH & BRAKE SWITCH  .
  49. Adjust brake switch. See CRUISE CONTROL RELEASE SWITCH & BRAKE SWITCH ADJUSTMENT  .
  50. Using a test light, probe between cruise control module assembly connector (harness side) terminals "C" (Gray/Black wire) and "E" (Black wire). See WIRING DIAGRAMS  . If test light illuminates, go to step 15). If test light does not illuminate, go to next step.
  51. Set parking brake. Raise drive wheels. Using a DVOM, measure voltage between cruise control module assembly connector (harness side) terminal "K" (Dark Green/White wire) and ground while rotating drive wheels. See WIRING DIAGRAMS  . If voltage is 0-5 volts, go to next step. If voltage is not 0-5 volts, go to step 53).
  52. Turn ignition switch to OFF position. Check for a poor connection or open in Dark Green wire (cruise disable output circuit) between cruise control module assembly and Powertrain Control Module (PCM). Reinstall cruise control module assembly. Connect scan tool to Data Link Connector (DLC). Using scan tool, command SMCC to ALLOW cruise. Clear any existing Diagnostic Trouble Codes (DTCs). Using scan tool, monitor SMCC INHIBITED display. Attempt to operate vehicle in cruise control. If SMCC INHIBITED is displayed on scan tool, go to step 56). If SMCC INHIBITED is not displayed on scan tool, go to step 58).
  53. Check for a poor connection or open in Dark Green/White wire (VSS output circuit) between cruise control module assembly and Powertrain Control Module (PCM). If Dark Green/White wire is faulty, go to next step. If Dark Green/White wire is okay, go to step 55).
  54. Repair poor connection or open in Dark Green/White wire (VSS output circuit) between cruise control module assembly and Powertrain Control Module (PCM).
  55. Check PCM. See appropriate TESTS W/CODES article in ENGINE PERFORMANCE section:
  56. Using scan tool, monitor the following parameters:
    • Vehicle speed sensor should be 25-100 MPH.
    • Trans range should be 2nd, 3rd or 4th gear.
    • System voltage should be 9-17 volts.
    • Engine speed should be 500-5400 RPM.

      If listed parameters are within range, go to step 55). If above parameters are not within range, go to next step.

  57. Perform appropriate POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See appropriate TESTS W/CODES article in ENGINE PERFORMANCE section:
  58. Turn ignition switch to OFF position, and then to RUN position. Clear any existing DTCs. Using scan tool, select Mode 4 diagnostics. Using scan tool, command SMCC to ALLOW cruise. Using a test light, probe between cruise control module assembly connector (harness side) terminals "H" (Dark Green wire) and "F" (Brown wire). See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step 60).
  59. Replace cruise control module assembly. See procedures in CRUISE CONTROL MODULE ASSEMBLY  .
  60. Check for a short to voltage in Dark Green wire (cruise disable output circuit) between cruise control module assembly and PCM. If Dark Green wire is faulty, go to next step. If Dark Green wire is okay, go to step 55).
  61. Repair short to voltage in Dark Green wire (cruise disable output circuit) between cruise control module assembly and PCM.
scientia non olet · About LEMON Manuals