Questions and Answers

Volkswagen Passat Cruise Control Q. Okay, here it is! 1994 Volkswagen Passat 2.8 liter V-6. Whenever I'm driving down the freeway, I engage the Cruise Control. In 15 minutes, while driving with the Cruise control on, my Check Engine Light comes on. I check to make sure this was consistent with the Cruise control. I did this a couple of times and every time the exact thing happen.

How does the Cruise Control work? Is the Cruise Control System work by vacuum? How can I resolve my problem myself?

Your help is much appreciated.
Thanks...

A. Here is a general description of how the cruise control works. Since all cruise control systems are, basically, the same, this applies to all makes and models.

DESCRIPTION:
The main parts of the cruise control system are the functional control switches, cruise control module assembly, vehicle speed sensor assembly and cruise control release switch, stop lamp and torque converter clutch (TCC) switch and a clutch switch on vehicles with a manual transmission.

OPERATION:
The cruise control system uses a cruise control module assembly to obtain the desired vehicle cruise speed. Two important components in the module assembly assist in this. The first is electronic controller and second is an electric or vacuum operated actuator. The controller monitors vehicle speed and operates the actuator. The actuator moves the throttle linkage, in response to the controller, to maintain the desired cruise speed.

The cruise control module assembly contains a low speed limit which will prevent the system from operation during speeds below 25 mph or 30 mph on some models. The operation of the controller is controlled by functional switches which can be located on the turn signal and headlamp switch, on the steering wheel or a separate arm, similar to the turn signal switch.

Cruise control release switch, stop lamp and clutch or clutch anticipate switch assemblies are provided to disengage the cruise system. The switch assemblies are mounted on the brake and accelerator and clutch pedal bracket. When the brake pedal or clutch pedal is depressed, the cruise control system is electrically disengaged and the throttle is returned to idle position.

Specifically, the cruise control in your Volkswagen Passat is vacuum operated. You can see the components involved in the block diagram below.

There is no real troubleshooting procedure other than hooking up the Volkswagen cruise control tester VAG 1466 to the system. The VAG 1466 pinpoints the problem. Since the malfunction causes the Check Engine Light to come on, there will be a code stored that is probably related to the problem.