Hi everyone, new to the forum and I'm hoping for some help. I am helping a friend who has a 2004 Jaguar X type. When you press the brakes her center light goes on but the right and left brake lights do nothing. I checked the bulbs and they are fine, checked for voltage on a multi meter and I get nothing (I believe it said .4 volts)
From what I read, the top light and the tail lights all use the same source so the problem couldn't be fuses or a brake switch. Assuming that is true I believe it is a wiring issue.
Anyone have any ideas how to diagnose and fix this?
I was thinking of testing for continuity but I'm not sure what points I should test. Any help is appreciated.

 

Does anyone have a wiring diagram for the brake lights? I tried searching but came up with nothing.

 

I don't know if you have an early 2004 (4 spoke air bag) or a later 2004 (rectangular air bag). Page one is for the early model - pages two and three are for the later model.

 

Thank you. How would I know if it's the earlier or later '04 model?

 

Early 2004 X-Type (air bag cover has 4 spokes)


Later 2004 X-Type (Air bag cover almost rectangular)

 

It is the later model (rectangular airbag cover). Based on the diagram I assume that since the high-mount stop lamp works then the fuses/relays or anything else related to the power source is working properly, can someone confirm that to be true? Is this strictly a wiring issue?
I have been trying to trace the cables to their source but have not had much luck. I started from the brake light bulb then removed the trunk liner, then removed the airbag cover which is between the pillar and the seat and stopped there. I'm not sure how much further I have to dig to find the connector, does anyone know? Am I better off just running a new cable from the high mount stop lamp to both bulbs in the tail lights?
Any ideas are greatly appreciated

 

pt80, when you measured the voltage, did you measure it in the light bulb socket, or did you go in the backside of the plug and measure it there? If you measured in the socket, I would recommend removing the plugs for the taillights and doing a good inspection of the connector. I bet you will find that the terminals are going to be corroded and that is causing your voltage drop. A few members here have had your issue and they almost all seemed to have this issue.

If you measured the voltage at the connector, then I would trace the wiring back on the passenger side of the car (assuming you are in the US, or the right side of the car if in question). Above the right rear wheel, the wiring should split out and go 3 different ways (each tail lamp and the hi mount stop). That would limit the scope of what you are dealing with to only that wiring which is inside the trunk.

If you need more help, let me know.

 

Hi Thermo,
I originally measured it at the bulb socket but yesterday I unplugged the connector and measured it there, still no voltage. Also, no corrosion.
I started to trace the cables, removed the trunk liner and the padding next to the seat and followed the cable down to bottom where the plastic cover is. I stopped there since I didn't know how much further I would have to keep going to see the split. My alternate plan was to run a cable from the high mount stop lamp to both tail lights but I much prefer to do this the right way.

Do you think the split will be under that plastic cover under the rear passenger door?

TIA, Andy

 

Andy, odds are, if you didn't find it in the trunk area, then you are most likely looking at the split being in the fuse box itself. Manufacturers normally do not split wires half way between 2 spots unless it is tapping off of something else (ie, a light half way or the like). In this case, I really doubt the wires run up to the 3rd brake light and then back down to the tail lights. So, there will be 3 wires running from the fuse box for the stop lights.

 

Hi everyone. I have to own up to my own stupidity sometimes, and this is one of those moments.
I was looking at the bottom inner bulb and replaced the wrong bulb. I was also tracing voltage for that bulb because the cable is white green.
In addition to feeling like a dope, I also spent hours tracing a problem that didn't exist. Those are the hardest to fix.

Thank you guys for your help, I'll be posting REAL questions later.

 

PT80, do not worry, we all make mistakes like that. I did something similar when trying to diagnose a headlight issue. I got the whole dip beam and main beam bit messed up and thought the main beams were the low beams as we call them here in the US. The big thing is that you figured out your problem in the end.

 

Yes, brake lights work. I now noticed a new squeak/creek which I will make a new post for later when I have more details. The car has 131k miles and its starting to show!

 

pt, post up where the squeak is coming from. Odds are, we can tell you where it is coming from. We are used to a lot of the creeks and groans the car makes.