When I turn on my headlights, the headlights come on. But not the tail lights. The tail lights do come on when I press on the brake, but they do not light up when I am driving at night time. In the daytime I am fine. I changed the bulbs its not that. Its not the brake light switch because the brake lights come on, and I can shift out of park. Could it be one of the relay's that's near the battery?

 

Have you checked the fuses? Tool box lid (underside) in engine bay lists which junction box they are in - boot, two in L/R Heelboards under back seat, can't remember others, but I'd give it a check.

You say the tail lights come on when you press the brake....when reading, I thought "means brake lights, they are separate" but later you refer to the brake lights by name....so if your tail-lights actually do come on with brakes it's probably not the fuse but something else going on - there's a light control module somewhere...but I'd encourage you to cover all the basics first - fuses, grounds, bulbs, etc.

 

Tail lamps are controlled via 2 separate relays in the Lamp Control Module located in the boot (trunk). There are separate circuits for left and right and separate fuses Fuse #5 5A in the LH engine bay fusebox for the LHS and Fuse #18 5A in the RH engine bay fusebox for the RHS. There are also separate earths for left and right sides.
It is unlikely that there are faults on both these circuits.
Both relays are controlled by the output from the Lighting section of the Body Processor Control Module on connection FC1-14 which is at 0V (ground) when the lights are on and +12V when they are off. This connects to the Lamp Control Module on connection BT21-17 so a good place to start would be to check if this point is at +12V with the light switch in the off postion and 0V with the light switch in the on postion. If not then you should perform the same test at the Body Processor Control Module output on FC1-14 to verify that this module is producing the correct output. The Body Processor Control Module is not as easy to get at as it is located behind the dash on the side of transmission tunnel on the passenger side (on UK spec vehicles) which is why you should check the easier to get at Lamp Control Module connection first in the boot (trunk).

 

Just a little hello from a fellow Irishman, ex Dub, based down in Kerry. Nice to see another major tax payer on here!

For what it's worth, my daily driver is a 96 x300 4.0l Sovereign, but I have a 97 3.2 Sovereign donor car, so if you ever get stuck for the odd part, give me a shout. Many bits are interchangeable between the 4.0l and the 3.2, but then again, many aren't! Tell us a little more about your car etc.

 

Thanks for the long detailed answer. How do I check if its the lamp control module?

 

Do you have any test equipment - a test meter or a test lamp and are you comfortable with how to use these and use wiring daigrams?
To be certain of the plug and the pin numbers to test we need to know the year and engine size of your Jaguar.

 

Sorry, I didn't put it down. 95 XJ6 4.0 Vin 7. I know how to use a test light

 

Start by downloading the X300 manual here My Files
Or go to the X300 'HOW TO' quick links and look for the link X300 Service Manuals 95, 96, 97 and click on it (this is the same locations as above).
This is a RAR type compressed file around 200 Mb in size. After you have downloaded it you will need to decompress it before it can be used.
You may already have a program that can do this or you can get free tools on the internet such as Winrar or 7 Zip. You will also need to have Adobe Reader installed to view the manual which is in pdf format. The files should be extracted by the program to the correct folders and all you need to do is to click the file called start.pdf to begin.

Navigate to
Electrical Guide - Sedan Range 1995
Wiring Diagrams and Descriptions
Fig 09.3 Tail Lamps; Rear Fog Lamps; Rear Side Lamps (page 97 of 183)

The rear lighting module depends on your VIN.
For VIN up to 739427 it is a Rear Lighting Control Module
For VIN after this it is a Lamp Control Module.

The wiring diagram for the 1995 vehicle shows this as the Rear Lighting Control module but you should confirm this using you VIN.
Either way, the module is located in the boot (trunk) although the pin references will be different

The instructions that follow refer to the Rear Lighting Control Module and not the later Lamp Control Module. The Rear Lighting Control Module contains separate circuits for LHS and RHS and uses separate power supplies as I mentioned in my last mail. Because these circuits are independent it is unlikely that this module is at fault but you need to check that it is receiving the correct input and it is easy to get at so it's a good place to start. The Rear Lighting Control Module is shown in the middle of the diagram. The control input is on the left of the module marked BT21-9 and the wire colour is shown as R (Red). The pin outs for this module are shown on page 24.

Check that your test lamp works by connecting it directly across the battery terminals.
Connect your test lamp between pin 9 in plug BT21 (it should have a red wire) and a good ground point (the battery negative terminal is nearby).
With the light switch OFF the lamp should light.
With the light switch ON the lamp should extinguish.
If you do not get the above then the Rear Lighting Control Module is not getting the correct input. This signal comes from the Body Processor Module and you will then need to test if it is producing the correct output.