2000 Discovery II. I just bought the truck a few weeks ago and noticed the cruise control doesn't work. there is an after market radio so the controls on the steering wheel for the radio doesn't work but I wasn't sure if that had anything to do with it.

 

Here's schematic and text of operation from the RAVE, our favorite volume of "Brit Lit" ( English majors take note ). The RAVE shop and owner's manual set is a free download below.

BTW, you'll be wanting to check your front drive shaft to see if it has grease fittings. Many did not, when they fail, they make a chirping sound, split apart, and spear a hole in the transmission. Write up on that and lots of other things in our tech section (see the D1 part of the forum, many things apply to both trucks).

 

Does the light on the master switch on the binnacle come on (pictogram looks like a highway bridge)? If so check the vacuum line that goes from the cruise pump to the actuator, they tend to get very brittle and disintegrate.

If the light is on and the vacuum line ok try unplugging the radio and see if that works. Believe it or not, speaking to factory radios, the wrong one can cause intermittent cruise issues. Literally no other symptoms except for the fact the cruise will randomly work and randomly cut out. If that solves the issue it's time to check the wiring of the radio. There's not an issue with putting in an aftermarket deck you just have to make sure only the "necessary" connections are made to the factory amp and no signal/communications link.

 

Truth. I've been having a problem with my factory radio suddenly making a loud popping noise and cutting out for a millisecond. The radio display never blanked, it was if the connection to the power amp under the seat was flakey but sometimes it would happen when motionless so I kind of ruled out a bad external connection. Because it was the easiest thing to try I bought another identical looking radio from a forum member and swapped it in. The radio worked great and solved the popping noise but I noticed that the cruise was now flakey. Intermittent activation and frequent failing at speed. I am so thankful to have found this forum thread because it saved me a bunch of unnecessary cruise troubleshooting.

I attribute the problem with the cruise to something related to the system which raises the radio volume related to road noise and/or wheel speed. I assume this radio doesn't support that feature and one of the vehicle's many ECUs is not happy about it. I swapped the original radio back in and the original problem came with it. Sound popping and cutting out but 100% functional cruise. The radio on the left is the original radio and the one on the right is the replacement which hampers speed control. Not many people are swapping in factory radios these days but I happen to like the originality and with an FM transmitter I have 90% of the functionality I need with regard to iTunes and Waze. If someone else goes down this same path and loses cruise, check your radio model #. The faces appear identical but the model numbers are indeed different. I'll post in the WTB section as well but if anyone is ditching their factory radio in favor of something newer and has a PUY radio they want to sell, please PM me.

 

You don't by any chance have the vacuum hose diagram, do you?

 

 

The typical cc failure is the vacuum hose from the cc pump to the vacuum diaphragm. Download the RAVE and find the pump under the hood. Replace the hoses and you should be good. You can also google search images. Let us know if that is not it.

 

Oh, almost forgot, could be a burnt out center brake light or a brake switch misadjusted under the dash - but most likely the vacuum hoses.

 

My cruise didnt work either - changed vacuum lines and no go.
I removed the vacuum pump and popped the cap off and the leads fell apart.

I replaced the actual vacuum pump for about $25 used and problem resolved.

If the light on the dash works, hoses are good, suck on the hose to the diaphragm and make sure it holds steady then replace the pump with a used one.