- Brake Light Switch: The brake light switch is responsible for sending signals to the cruise control system when the brake pedal is pressed. If the brake light switch is faulty or has a loose connection, it can prevent the cruise control system from engaging or maintaining speed. Check that the brake light switch is functioning correctly and that its electrical connector is secure.
- Speed Sensor Failure: The speed sensor detects the vehicle's speed and transmits this information to the cruise control system. A malfunctioning or damaged speed sensor can lead to inaccurate speed readings, causing the cruise control to malfunction or not work at all. Check for any issues with the speed sensor, like a loose connection or a faulty sensor.
- Cruise Control Module: The cruise control module receives and processes signals from various components, including the speed sensor and the brake light switch, to control the cruise control system's functions. If the cruise control module is faulty, it can cause various problems, including the cruise control not working. Have the cruise control module inspected for any electrical issues or internal failures.
- Cruise Control Switch: The cruise control switch on the steering wheel is responsible for engaging and disengaging the cruise control system. Sometimes the switch itself can become faulty or dirty, leading to the cruise control malfunctioning or not responding. Check the cruise control switch for any damage and ensure that it's clean and making good contact when pressed.
- Electrical Problems: General electrical issues, such as loose or corroded wiring connections, blown fuses, or faulty relays related to the cruise control system, can also disrupt the system's functionality. Inspect all electrical components related to the cruise control, including fuses, relays, wiring harnesses, and grounds.
- Vehicle Speed: The cruise control in a 1999 Nissan Altima operates within a specific vehicle speed range. If the vehicle's speed goes below or above the permissible range, the cruise control will automatically disengage. Check your vehicle's speed and make sure it's within the recommended range.
- Faulty Throttle Body: A faulty throttle body or a vacuum leak in the throttle body area can cause the cruise control to malfunction. Check for any issues with the throttle body or related vacuum hoses and ensure they are functioning correctly.
If you've checked these common causes and still have issues with your 1999 Nissan Altima's cruise control, it's best to consult with a qualified mechanic or a Nissan dealership. They can diagnose the specific problem accurately and perform the necessary repairs or replacements to restore the cruise control's functionality.
