Jump to content

1999 cruise control fault finding?


Countax
 Share

Recommended Posts

Just extended my LR fleet with a 1999 4.0L range rover. Everything seems functional except the cruise control. Pls can someone advise the fault finding process i can go through to locate the fault and also where the parts are such as vacuum lines etc as i don't yet have the Haynes manual.

Thx,

Nigel

Link to comment
Share on other sites

There's a fault finding procedure for it in the official workshop manuals - don't think the Hayneous manual is particularly helpful on this topic, from memory.

The vacuum pump lives on the nearside wing, actuator is on the throttle bracket on the plenum. One pipe between these. Another pipe runs across the bulkhead and through it above the pedals - this is attached to a valve on the break pedal that releases the vacuum if you break (as well as the cruise ECU being linked to the brake light switch. The ECU itself is tucked up on the top left of the drivers footwell. It uses the speed transducer (on the transfer box) to monitor the vehicles speed. There are two buttons on the steering wheel which can have dodgy connections (they go through a spring type connector thingy at the back of the wheel).

Any and all bits of it can and do cause problems... :rolleyes:

If your speedo works your transducer itself is okay, just need to check that there's a signal at the ECU. Leaky pipes are the most common cause of problems - they split with age, as does the actuator sometimes.

My old rangie had already had a replacement vacuum pump when I got it. I replaced all the pipes (they were perished), checked everything out carefully going through the diagnostic procedure but never got it to work reliably. It got gradually worse and eventually stopped working at all.

According to the diagnostic procedures when all other causes have been eliminated it's the ECU at fault, and there does seem to be a fair bit of anecdotal evidence for them failing pretty frequently. They're quite cheap on eBay, but how many of them are in working order is anyone's guess.

Link to comment
Share on other sites

Geoffbeaumont,

Are you talking Classic or 38A?

Comments like "don't think the Hayneous manual is particularly helpful on this topic, from memory", and 'ECU's available on Ebay' suggest Classic, whereas the question is about a '99, therefore 38A.

I'm just clarifying, not complaining.

Cheers

Link to comment
Share on other sites

Its a P38a version so if Geoff is refering to a classic RR how much of it is similar to my vehicle?

I also think the heated mirrors, seats and rear window may not be working so maybe is a more centralised control fault. Any advice is appreciated.

Thx,

Nigel

Link to comment
Share on other sites

Geoffbeaumont,

Are you talking Classic or 38A?

Comments like "don't think the Hayneous manual is particularly helpful on this topic, from memory", and 'ECU's available on Ebay' suggest Classic, whereas the question is about a '99, therefore 38A.

I'm just clarifying, not complaining.

Cheers

Errr - you've got me there. Really should read a little more carefully... :blush:

Nigel - I don't know how of the P38a system is the same as the classic. At a guess the speed transducer probably is, but I doubt anything else.

Link to comment
Share on other sites

Errr - you've got me there. Really should read a little more carefully... :blush:

Nigel - I don't know how of the P38a system is the same as the classic. At a guess the speed transducer probably is, but I doubt anything else.

Geoff,

Many thx for your help. I downloaded Rave last night and it has a pretty good explanation of the CC system so i will start diagnosing this weekend.

Nigel

Link to comment
Share on other sites

The vaccuum pipes that operate the cruise control on these is the usual problem. Usually split near to the actuactor on the LH wing behind the air suspension valve block/compressor box. I'd check the pipes first, easy fix if they are split.

Link to comment
Share on other sites

The vaccuum pipes that operate the cruise control on these is the usual problem. Usually split near to the actuactor on the LH wing behind the air suspension valve block/compressor box. I'd check the pipes first, easy fix if they are split.

Marc,

thx for the advice. i will check this out at the weekend.

Nigel

Link to comment
Share on other sites

The vaccuum pipes that operate the cruise control on these is the usual problem. Usually split near to the actuactor on the LH wing behind the air suspension valve block/compressor box. I'd check the pipes first, easy fix if they are split.

Fixed it !....Marc you were right. The small vacuum pipes near the actuator were perished. Replaced them and its working fine.

Nigel

Link to comment
Share on other sites

  • 4 weeks later...
Just extended my LR fleet with a 1999 4.0L range rover. Everything seems functional except the cruise control. Pls can someone advise the fault finding process i can go through to locate the fault and also where the parts are such as vacuum lines etc as i don't yet have the Haynes manual.

Thx,

Nigel

I have a disco 1, my cruise control kept dropping out or refusing to be set, I eventually traced it to the switch above the brake pedal. I figured out if I lifted the brake pedal up by putting my foot underneath it the cruise control worked ok. The problem appeared to be play in the bearings of the pedal, rather than stripping out the pedals (which in the enclosed space looked like too much trouble!), I made a U shaped piece of thin steel, that fitted over the metal of the brake pedal, I pinched this so it was a tight fit, then pushed it on the pedal by the cruise control brake sensor switch, I put a bit of tank tape over it to fix it, and its been ok ever since.

Regards Derek.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

We use cookies to ensure you get the best experience. By using our website you agree to our Cookie Policy