Cruise Control Gone Again

Hi

just joined this forum I've got a S reg 1998 2.0i 16v VSX auto saloon.Everything is going good except the cruise control again,the first time it was the vacuum tube perished undef the wheel arch,second time it was the contacts on the brake pedal,now its gone again, where is the next place to look?

TIA

Hi bosscat,

Welcome to Club-XM. I hope you find the site friendly informative and useful. One of the quickest ways to figure out whats wrong is to have the ecu plugged into the diagnostic computer and it will tell you which sensor is faulty. Do you know of anyone with an Elit, Saouris or Lexia computer? maybe a friendly garage? If not, then its a matter of disconnecting the plugs from the engine ecu and testing back to each sensor in turn to check for continuity or proper operation.

cheers

noz

ps
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Hi Bosscat

It is also worth checking the 3 column stalk fixing screws. The holes in the plastic lugs on the switch body are larger than the screw shanks. If they work a little loose (they only screw into plastic) the lever just moves the whole switch and fails to operate the contacts. In this state all the other tests find no fault.

Regards

XMexc

thanks for the help so far,stalk looks OK,still looking for a simple solution,does the cruise control have a relay?should I here a click when turning on the dashboard switch?l

My CC was intermittent - you just never knew when it would work and when not.

I removed and cleaned up all the contacts on the relays behind the headlamps due to a cooling fan problem & coincidentally I've never had trouble with the CC again.

I seem to remember there is a specific CC relay behind the drivers headlamp.

Hi Bosscat

There are at least two types of XM cruise installation. The 2.5TD's and possibly some other later models have a fly by wire accelerator control with an all electronic cruise using the main ECU . The other cars have the same set of switches but a dedicated cruise ECU and control relay. In this latter installation first used in some of the top of the range Mk1 XM's the cruise electrics/electronics operates a vacuum cylinder that is mechanically joined to the operating lever of the engine injection system.
From your comments about the loss of vacuum in your previous cruise problem I guess you have the earlier more complicated system. Have seen a number of requests for details of this system but sorry have not seen a reply that pinned down the location of the cruise ECU and relay.

Regards

XMexc

This exact problem was covered in the CCC magazine for September 2006.
Try finding someone with a back issue near you!.
If it is not the vacuum tube then check the solenoid valve behind the passenger side wheel arch. This should click when 12V is applied....
It is a good article - 5 pages.

Steve.

Can anyone do me favour and post this article on theses pages sounds to me it could be the answer to my problems!

You could also look at the nylon bush which connects the vacuum unit via a rod to the throttle linkage. The bush on mine perished enough that the rod would pop out and hang down. I fashioned a replacement from an aluminium window runner wheel from the local hardware store. Never had a problem since.

Hi, i run 2 xm 2.1td's auto's, a 94 exclusive and a 2000 vsx both mk2 and both have exhibited inttermittant failure of cruise and not surprisingly the same fault. The cruisecontrol computer is mounted with all the other ecu's in the box on the inner r/h wheel arch. it's approx 6"x4"x2" with a single 15 pin black connector.
You will need a multimeter - nothing expensive-but one with a digital display is easier to read and gives greater confidence in readings.With ignition off gain access to and remove connector from ecu.
STEP 1. turn ignition on, gearbox in neutral and set cruise contol switch to on, with meter set volts dc check for 12 volts on PIN 10 if ok swich supply ok.
2. same conditions check for 12 volts at PIN 9 IF ok gearbox reverse relay ok, if not trouble shoot reverse relay circuit and brake pedalswitch ( OR USING DOMESTIC 15 AMP FUSE WIRE ISERT A SMALL LENGTH BETWEEN PIN9&10 ON CONNECTOR, RECONNECT AND TEST DRIVE)
3. check for 12 volts dc at pin 5 when brake pedal is depressed, if not troubleshoot brake switch circuit
4. ignition off.meter set to resistance (OHMS) check coloumn swich, using pin 3 as common check resistance when stalk is moved to increase /decease at pin 6. check disengage function between pin 2 and pin 10,any anommalies here and remove stalk switch, it can be opened up and contacts realigned.
5. using local earth as commom,check resistancefrom pins 1,6,7,8 any anommalies here are vacuum pump/solenoid/ earth related

That's very useful Robert, thank you.

Derek

Hi Derek, Robert and all

I'd like to second Derek's thanks. I'll be out with the tester on mine tomorrow !!

Mike.

thanks for the info guys, trouble is ,in the best XM tradition the cruise control and the speedo are now working perfectly. I'll have a go with my multi meter when they pack up again.

Just thought I should add - a previous 2.1TD Auto of mine had the ECU tucked up the side of the dash down near the drivers footwell. I think it had been added as an afterfactory unit as the elctrical connectors for the stalk switch were crimp ons. Everything else was correct though.

I should have posted earlier, but better late than never.

Just to say that robertmnorton's magic trick of bridging between pins 9 and 10 on the CC controller plug did the business for me.

Derek