Here's a breakdown of the common causes and troubleshooting steps:
1. Check the Fuses:
* Locate the fuse box: Your owner's manual will show you the location of the fuse box(es) (often under the hood and inside the cabin).
* Identify the cruise control fuse: The manual will specify which fuse is for the cruise control system.
* Inspect the fuse: Look for a blown fuse (broken filament). Replace it with a fuse of the same amperage if necessary. If the fuse blows again immediately, you have a short circuit somewhere in the system and need to proceed to further diagnosis.
2. Inspect the Cruise Control Switch (Steering Wheel):
* Test the switch: Carefully examine the cruise control switch on your steering wheel. Look for any visible damage, loose connections, or broken components. You may need a multimeter to test the switch's electrical continuity (refer to your repair manual for instructions).
* Clean the switch: Sometimes, corrosion or dirt can interfere with the switch's operation. Try cleaning the switch contacts with a contact cleaner.
3. Check the Vacuum System (if applicable):
* Many older vehicles use a vacuum system for cruise control. A leak in the vacuum lines can prevent the system from working correctly.
* Inspect the vacuum lines: Carefully inspect all the vacuum lines connected to the cruise control system for cracks, leaks, or loose connections. Replace any damaged lines.
* Check the vacuum pump (if equipped): The vacuum pump maintains the vacuum needed for cruise control. A faulty pump can also cause issues. This is more likely to be diagnosed by a mechanic.
4. Examine the Brake Switch and Clutch Switch:
* These switches are safety features: If they're malfunctioning, the cruise control will disengage.
* Test the switches: Use a multimeter to test the continuity of these switches. Replace them if faulty.
5. Check the Speed Sensor:
* The vehicle speed sensor (VSS) is crucial: The cruise control relies on the VSS to maintain speed. A faulty VSS will prevent cruise control from functioning.
* Testing the VSS requires more advanced tools and techniques. You might need an oscilloscope to test its signal. This is usually best done by a mechanic.
6. Inspect the Cruise Control Module (CCM):
* The CCM is the brain of the system: A faulty CCM can cause various cruise control problems.
* Testing and replacing the CCM requires specialized tools and knowledge. This is generally best left to a professional mechanic.
7. Wiring Harness Inspection:
* Check for broken or corroded wires: Carefully inspect the wiring harness connected to the cruise control system for any damage. Repair or replace any damaged wires. This requires carefully tracing the wires using your repair manual's wiring diagram.
Important Considerations:
* Safety First: Disconnect the negative battery cable before starting any electrical work to prevent accidental shorts or shocks.
* Professional Help: If you're not comfortable working with automotive electrical systems, it's best to take your Lumina to a qualified mechanic. Misdiagnosis or improper repair could damage other components.
* Diagnostic Scanner: A scan tool (OBD-II scanner) can sometimes provide codes that pinpoint the problem. While not always helpful for cruise control issues, it's worth a try.
By systematically checking these components, you'll increase your chances of successfully diagnosing and repairing your Lumina's cruise control. Remember, patience and a good repair manual are your best allies in this process.
