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Rock Sam

Rock Sam 5/8/2018

2008 Hummer H3 Base 5 Cyl 3.70L


Diagnose cruise control problems in my car?

1 Answer

Wondermachanic Canada

1. A short or electrical overload in the cruise control circuit may have caused the power supply fuse to blow. Refer to your owner's manual for the location of the fuse.

2. Faulty brake pedal Step on the brakes to see if the brake lights come on. No lights could indicate a faulty
brake pedal switch if the brakes and cruise control share the same switch. If the parking brake or switch is
maladjusted it will prevent the cruise control system from engaging.

3. The cruise control system can't function without a good speed input. A bad VSS will also prevent the
speedometer from working.

4. If the speedometer is reading normally, you can probably rule this out as a possible cause.

5. If some of the cruise control buttons work, but others do not, chances are the problem is in the switch. If
none of the buttons work, chances are the fault is in the wiring.

6. Repairing the wiring or replacing the switch will require removing the steering wheel.

7. If the Check Engine Light is on, and you find a code related to the cruise control system, the code will give
an indication of the nature of the fault.If a cruise control code indicates a module fault, check the power and ground connections to the module. If that is not the problem, you will need a replacement module from an
auto parts store.

8. If you have an older vehicle with an electromagnetically cruise control system, failure of the diaphragm
inside the vacuum actuator or a faulty vacuum control solenoid can prevent the actuator from operating
normally.There is no way to rebuild the unit, so it will have to be replaced if defective.

9. If the motor that opens and closes the throttle is bad, the engine probably won't' run above idle. The Check Engine light should also be on, with codes set for the throttle actuator motor or throttle control system.


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