RE: XJ40 1989 Sovereign,
What is the procedure to reset the warning display for low brake pressure etc on the dash, the brakes have been fixed but still warning system on, haven't worked on this dash before, any clue will do also is there a code reader connection for this model & location? i have a code reader that suites models 90's on.....thanks

 

I am not sure whether you mean the dash brake light or that there is a code still being displayed in the odo window. If you have a code still showing you can just unhook the battery for a few seconds to clear it. If the code comes back then there is still a problem. As always, make sure you have your radio access code handy before unhooking battery! I think that all these cars use the OBD I which displays the codes through the odometer window. I don't think you need a separate reader for them.
My white car would flash the brake warning light without a code whenever I applied the brakes. I cured it by bleeding the brake system completely. good luck.
*Disclaimer- I could be dead wrong on all these points.

 

Jerry,
thanks for your response, i finally got to see the car yesterday as the info was passed onto me via phone, the info about low brake pressure/low brakes warning/ seat belt ect is displayed in the trip meter display R/H/s of the steering column section R/H/drive car, this display will show trip meter as well, there is a "clear & VCM " button with several others, you can use the clear button to change the display but eventually the warnings come back, brakes have been replaced, system bled completely yet still low pressure warning even though the brake system is in new condition, any suggestion to get rid of those warnings will be helpful.
Should we be looking at the ABS in relation to low brake pressure? Also is there a diagnostic socket if so what shape and location? i don't have a workshop manual for the XJ40 only XJ6 and Sovereign (Oct 86 - Sept 94) D to M an all earlier manuals as i reconstruct the colour wiring schematics....any help would be greatly appreciated as the owner is new to jaguars, he loves the car but don't want him turned off over a couple of annoyances ........

 

Ok, Well the clear vcm button doesn't clear the codes, you have to disconnect the battery to do that - but re-read Jerry's post above for precautions etc before disconnecting!

The diagnostic socket is located under the battery tray on battery in the boot models but it will be of no use to you if you don't have or have access to the Jaguar PDU (which AFAIK very few people have, not even the dealers anymore)

All codes are accessed through the LCD display - to display them, (if there are any remaining) switch the ign on, don't fire up the car and press the VCM button.

HTH

Larry

 

Ok, I think I still don't understand. The xj40 designation is for cars 87 thru 94, even though they are referred to -and labelled- as xj6 and such like also. If I read this correctly, you have a fault code being displayed in the odometer window. There is a listing of codes showing the probable causes in the TSB section of this (xj40) forum. It is also printed in the ever questionable Haynes manual. I cant figure what "low pressure" in the brake system might mean other than if the antilock system were trying to work. But if it were you would likely have more than just a code or light to point your way. Good Luck.

 

Hi xjtom,

The brake power assist system in the XJ40 is operated by pressurized hydraulic fluid rather than the more conventional engine vacuum. Hydraulic fluid is stored under high pressure in an accumulator sphere in which a charge of nitrogen is separated from the hydraulic fluid by a diaphragm. Given your symptoms, I would suspect that either the accumulator has failed (very common), or there is a problem with the low pressure warning switch or its electrical circuit. However, there are other possibilities.

I am attaching the Power Hydraulics manual, which has a complete description of the system and diagnostic flow charts that will help you track down the cause of your symptoms. Note that your '89 may have been originally equipped with the self-leveling rear suspension (SLS). Most of these systems have been retrofitted with a conventional coil/shock setup and the hydraulic lines that fed the SLS have been blocked off, but it is remotely possible that your car still has the SLS.

Please keep us informed.

Cheers,

Don

 

Don,
thanks for the file i will have a good read later, the warnings aren't a # code, it scrolls through bottom right hand side of the dash along with other info such as: fasten seat belts - hand brake on etc, the clear and vcm can switch between the trip meter info and this warning info as it's described in the hand book but no suggestion on how clear the warnings, what the history of the car is i don't know, a club member friend bought it and wanted me to see if i could get rid of these warnings about brakes, as mentioned extensive brake work done but i didn't see what and who did it........did the disconnect battery but all came back and no effect on the radio (after market type)i'll try keep you all up to date, thanks for the responses