Problem:  Cruise control stopped working suddenly, and failed to work afterwards

Solution Difficulty:  Moderate

Few things are more annoying that losing your cruise control. I was on my way back from Wilmington, NC with the cruise set, when all of a sudden, it just dropped out and my car began decelerating rapidly. I fiddled with the system, but to no avail. The system was down.

I went on the Internet and found very little information about this problem. However, after a few months I decided to investigate further. So I cracked open my Bentley manual (CD actually), and started doing diagnostics.

With a little bit of research online I found three possible causes of a cruise control failure. Apparently, the VW cruise system is an isolated vacuum system, which means that if you lose negative pressure, you won't notice any sort of check engine light or a badly running engine. The three main causes of failure were:

• A leak in the vacuum line
• A bad micro switch (connected to brake pedal and clutch pedal in manual transmission cars)
• A bad vacuum pump.

It is also possible that your electronic control module could be bad, but this should be a last case scenario for you since it's hard to physically access.

There are several ways you can test the system. The first thing I did was remove the interior trim and gain access to the micro switches. I check to make sure the switches weren't engaged when the pedal wasn't depressed. This can happen if the clutch or brake pedal starts to sag, and will open the valve and release the vacuum on the line. (which shuts off the cruise control). I temporarily pulled the vacuum line and attempted to test it with a hand powered vacuum pump. I was not able to apply any vacuum to the line.

Since everything appeared to be ok with the switch, I moved on to checking the cruise control solenoid, which requires you to remove the top engine cover. I attached my vacuum pump/gauge to this hose and tried to add vacuum to the system. Again, nothing.

So I began the slightly time consuming task of accessing the vacuum pump. Since the pump is located beneath the ABS system, you must access it from inside the driver side wheel well. I jacked up the car, removed the wheel and then unfastened the wheel well liner and pull it back behind the suspension. From here, I could clearly see the pump. I removed the pump by compressing the rubber mountings, and detached the vacuum line.

I was concerned that there could be a break in the vacuum line, and that replacing it would require pulling new line through the firewall. Luckily, when I attached the vacuum pump to the line and tried to pump the air out of it, it held a vacuum. Leading me to the conclusion that the pump was bad.

Now I would like to note that previously when I tried to check the vacuum line, I had the car running and the cruise control in the ON position. I'm not sure, but regardless, the line held vacuum when I tested each individual valve.

The other possible cause could have been a bad electronic module. You can access this by removing the lower brace, and shining a flashlight toward the firewall. The module you are looking for is 213, and it should be black. I've read one account of a guy who actually rebuilt this module, but the vast majority of people just replace it. (about $200-$300 I believe).

It is also possible that the switches in the control stalk are bad. This is the small attachment on the side of the steering column that houses the cruise control switches. Apparently, there is a procedure in the Bentley manual that allows you to jumper the control module plug and check these switches. I did not run this diagnostic since it was unnecessary in my case.

Recently I spotted a VW vacuum pump on EBAY for $15. It was for a different model car, but I'm pretty sure it was the same specifications as the one the B5 Passat uses. I've yet to replace the vacuum pump as I live in the city and since the original failure I've made very few long driving trips. I may replace the pump at some point since it's a matter of simply putting it back inside the car and hooking up the tubes.

This article contributed by ERSWeb
Read more by this author at http://ElectronicRealitySolutions.com