Is your dub’s cruise control giving you trouble? Instead of Fahrvergnügen, are you getting annoyed with your cruise control system? Here’s some info that might help.
First, let’s get a couple of things out of the way:
- Cruise control doesn’t always work the way everyone thinks it should
- Because of this, sometimes ‘broken’ cruise control isn’t broken at all
So step 1 is to verify that your system isn’t working correctly.
How Cruise Control Is Supposed To Work
The speed is selected by pushing the SET button on your steering wheel, and the vehicle should stay at this speed until you tap the brakes, accelerate for passing, choose a different speed or hit the OFF or CANCEL button.
When you press RESUME after you have decelerated, the control will take you back to your last selected speed. You may use the accelerate (+) or the decelerate (-) buttons to increase or decrease your select speed.
- Cruise control typically does not work unless you are driving at least 30 mph, and will not work if you’re in a low gear. It also doesn’t usually work at high speeds (over 90mph).
- Cruise control won’t resume automatically if you hit the brakes, even you touch them accidentally. Same goes for the clutch (if you have a vehicle with a manual transmission, obviously).
- The cruise light indicator will stay lit even if cruise control isn’t actually engaged.
- Cruise control doesn’t mean your car will stay at the same speed no matter the terrain. If you’re driving in the mountains, for example, cruise is going to have trouble maintaining speed.
If your VW’s cruise isn’t doing any of the things it should, and none of the notes apply, than odds are something is wrong.
Adaptive Cruise Control Function and Diagnosis
The adaptive cruise control system does more than maintain a speed, it also has the ability to determine traffic flow and distances in order to adjust the speed to meet the circumstances. It is a laser-based system that has a front mounted laser that continuously monitors and reads the distance in front of the vehicle in order to determine whether the speed needs to be adjusted.
With the adaptive cruise control system, it interacts with both the throttle and the brake as it accelerates and decelerates. The system works through data that is retrieved and shared by way of sensors and computers. The range finder on the laser delivers information to the cruise control module, which uses that information to calculate the proper distance to follow after considering speed and throttle position, as well as the brake status. All of this must be functioning in order for the system to work.
If communication fails in any of the different sensors and systems, the entire cruise control will fail. When it fails, it will produce an engine trouble code. So if you’ve got a problem with your adaptive cruise control system, try pulling codes with your code reader.
Older VWs Only – Electromechanical Cruise Control Function and Diagnosis
This older system has a vacuum actuator that is connected to the throttle linkage, which is used to open and close the throttle in order to maintain the speed. The connections can be a ball chain, linkage or cable. The actuator pulls the linkage, which opens the throttle in order to increase speed if you come upon a hill. The actuator loosens the linkage for less throttle when going down a hill. You coast until you need more throttle.
Electronic Cruise Control Function and Diagnosis
If your Volkswagen has an electronic throttle control, it has an electronic cruise control. The switch on your steering column or steering wheel lets the Body Control Module (BCM) know what speed you want, and then the BCM sends that information on to the PCM. Your system may bypass the BCM, but the information needs to go to the PCM in order for the cruise control to work.
The PCM reads what speed you selected and compares it to the speed reading it gets from the vehicle speed sensor, and then it determines the amount of throttle to apply to get the speeds to match. It then gives the actuator motor a command to open or close the throttle to get to the right speed and RPMs. It also monitors the transmission in order to determine which gear it is in, and it knows what position the brake pedal is in as well. If it is a sophisticated system, it will also look at the ABS or stability control system.
When you use your cruise control, the PCM reads the throttle or pedal to maintain the right speed. If you accelerate to pass, you override the cruise control until you let off the gas. Then the vehicle decelerates to the proper speed.
Standard Cruise Control System Components
Here’s a recap of all the basic components of cruise control systems. Understanding how these components interact with your specific vehicle’s system will help you find your problems, so if you’re not sure about one of the components below, be sure to review the section above that applies to your VW.
- Module – if it is not incorporated into the PCM
- BCM – if all inputs are sent here from the steering column or wheel before going to the PCM
- Clutch pedal switch – on a manual transmission
- Brake pedal switch – at the top of the pedal
- Vehicle speed sensor
- Actuator – motor on an electronic system and vacuum on an older system
- Indicator lamp for the dash
Cruise Control Issues
Cannot Engage the Cruise Control
Your Volkswagen cruise control will not work if you have any of the following conditions:
- Your vehicle speed sensor is not working. If this is the case, your speedometer will not be working either.
- Your throttle position and engine speed do not match the input position.
- You do not have enough volts going to the PCM or other parts of the system.
- You are in PARK, REVERSE, LOW or NEUTRAL gear.
- Your clutch pedal is depressed/disengaged.
- You are driving less than 30 miles per hour.
- Your traction control system or ABS has been engaged for more than a couple seconds. This can vary.
- Your vehicle speed is too high. Some systems will not operate over 90 m.p.h. for safety reasons.
- You have your foot on the brake pedal.
- Your VW’s system detected an error and gave you a code. This can keep the system from working until you read the code and make repairs.
Common Cruise Control Faults
Fuse – Check your owner’s manual to see where the fuse is located and check the fuse. Replace it with the proper fuse. If the new fuse blows as soon as you engage the cruise control system, you could have an electrical short. Use the wiring diagram and an ohmmeter/voltmeter to find the short.
Brake Pedal Switch – Put your foot on the brakes and make sure they work. If you have no brake lights, you may have a switch problem. The same is true for the parking brake. Since the cruise control is tied into the brake system, if it reads that the brakes are on, it will not engage.
Vehicle Speed Sensor (VSS) – If the VSS is bad, it cannot give accurate speed readings. This will affect the cruise control and the speedometer. If the speedometer is reading accurately, then the VSS is probably not the problem.
Cruise Control Switch – The switch is either on the steering wheel or on the column. If some of the buttons work, but others do not, it is probably a bad switch. If none of your buttons work, there could be a short in the wiring between the switch and the PCM. You can check this by removing the steering wheel. Before you do that, make sure you deactivate the air bag system by removing the fuse and waiting at least 15 minutes.
Cruise Control Module or PCM – You may see a Check Engine Light when you have a faulty module or PCM. It will trigger a code that will help you determine where the problem is at in the system. If the module is the problem, check the ground and the power connections. If there is no problem there, you need to replace the module.
Vacuum Actuator – The diaphragm on the inside of the actuator can become damaged or there may be a leak in the vacuum system. It could be a bad control solenoid that is keeping the actuator from working properly. You will need to replace the unit.
Throttle Actuator – If your VW has an electronic throttle control, you may have a bad motor in the actuator. If it is not opening and closing the throttle, your engine is probably not running above an idle. You will also see the Check Engine Light, and there will be codes that indicate the throttle actuator motor or control system have problems.
When your cruise control system is on the verge of failing, it starts to give you problems. Here are some of the problems you may see before it fails completely:
- Trouble engaging or disengaging your cruise control
- Intermittent brake lights without you using the brakes
- Brake lights not coming on when you are using the brakes
- Trouble shifting out of PARK with your foot on the brake
Your Volkswagen cruise control is an important part of your driving experience, and if it starts to give you trouble, you want to get it repaired immediately so you can continue to enjoy driving.