cruise control problem started the day I bought the disco, actually on my way home when it went out, I read posts on here about checking the vacuum lines and did that, today I went 1 step further and powered up the vacuum pump (applied power directly to the pump) and it turned on I then applied power to the solenoid on the pump and it started to pull the accelerator actuator as it should so I know my vacuum lines are perfect. so where should I look now? I tested the power button, and the 2 steering wheel control buttons at the cc ECU and they are all working. I have not tested the speed sense wire and I am not sure how to know if the cc ECU is properly operating the pump. I noticed there is a relay (shutoff relay?) on the schematic but not sure what might trigger this relay if anyone has a better idea of where my problem may be I would really appreciate it. I have a trip to Vegas coming up and would prefer the CC working while I am on the road for 5 hours.

 

I dont know where you would go from here. This is very weird.

 

I am having the same problem with mine. I checked all my vacuum lines and even changed out the vacuum pump with a used but working one. Still nothing. I am beginning to think the problem may lie in the ECU itself. I have a new set/resume switch that I am going to throw in when I get home but really don't think it will fix the problem.

If you figure out what is going on let me know so I can maybe fix mine too.

BTW, Denver to Phoenix with no cruise control sucks a lot.

 

mine doesn't work either in an 03

 

OK so the other day I found a post on here about testing procedures for the CC system (which I thought would be great since it tells how to power up and test the whole vacuum system) the wire colors were wrong but all the pin locations were correct. I tested everything that was on this sheet and everything works as it should (the good news is the vacuum pump, solenoid, and switches all seem to work fine, the bad news is according to this sheet the problem is in the ECU). I decided to go one step further and double check all the schematics for the system on the rave cd and found one big discrepancy that sent up a flag, pin 9 at the ECU (at least from my understanding) should have power when the vehicle is in a forward or reverse gear and the brake is not applied. I put the car in drive and released the brake and this wire was not powered! not sure if I have a problem with my neutral safety switch or not but checking this out will be my next step. anyone else who is having the same problems I suggest looking back for the post about testing the CC ECU as these tests will rule out many posibillities of faulty switches or vacuum systems.

 

maybe someone with some knowledge of the brake pedal itself can answer this question. how does the vacuum line on the brake pedal tie in to the CC system, my guess is it is just a pressure release valve tied in so if you hit the brakes while the vacuum is engaged and the CC is accelerating it will release the vacuum and the CC will instantly stop accelerating (at the same time the CC ECU will receive a signal from the electric brake switch and turn off the vacuum pump solenoid until the resume button is hit)

 

so I found the reason why pin 9 was not powered, the 2 wire plug on the brake valve switch came off, but now that all wires at the CC ECU are working as they should, the CC system is still not working. I pulled the ECU out and opened it up to see if anything is visibly wrong but I dont see any burnt traces or components on the board so I may try to find a cheap replacement ECU if I can.

 

While waiting for the next SUper Bowl commercial I stumbled upon this.
http://www.jewellamberoil.com/sales/...roducts_id=199

 

Got a wild hair while driving across town tonight and decided to try the cruise control again. Much to my surprise it worked this time. No idea why it worked but it does. Must have hit the right bump while playing on Four Peaks.

 

My cruise control stopped working right after I had the front prop shaft replaced by the dealer. Not knowing if there's a connection, I didn't go back. Might there be or is it just coincidence? I know on another vehicle I had, there was a speed sensor down in that area, but I have no idea with the Disco. I just want to be informed if I talk to the service guy.