Speed Control System — Description and Functionality Check (Chevrolet Trailblazer 1)

1. The cruise control system ensures that the vehicle maintains a set speed. The system components include an electronic control unit (ECM), a servomotor, a brake pedal position sensor (BPP), switches, and wiring that connects these components. The design of this system does not include mechanical or vacuum connecting elements. When diagnosing some elements of the system, it is necessary to use special equipment and perform special procedures, the description of which is beyond the scope of this manual. Therefore, only some general diagnostic procedures are described below, during which it is possible to determine the source of the malfunction.

2. Inspect the fuses (see subsection 3).

3. The system is switched off via the brake pedal position sensor (BPP) (or brake light switch). When checking the functionality of the brake lights, have an assistant turn them on and off during the test (when voltage is applied to the brake light switch, the cruise control system is turned off).

4. If the brake lights do not come on or continue to come on after you release the brake pedal, troubleshoot the problem and recheck the cruise control system.

5. Inspect the wiring between the PCM and the servo motor for open or short circuits. If necessary, restore the chain.

6. The operating parameters of the system come from the PCM, as well as from the vehicle speed sensor located in the gearbox or transfer case housing. The vehicle speed sensor (VSS) is described in detail in Chapter 6.

7. Test drive the vehicle to ensure that the cruise control system is working properly. If the system is not working properly, contact a service station to identify and repair the problem.