I have a 1997 XJ6.
Okay so I got my last issue fixed. Replaced the alternator and she purrs like a kitten now. So on to the next issue!

My brake lights have stopped working ( the break bar in the rear window still works), my gear shift is stuck in park ( I can manually move it by sticking a screwdriver in the release), my signal lights don't work, and when I press on the brake pedal there is no click. Also, the brake lights don't flash when I set the alarm.
I have checked the truck fuses and they are fine. What could be causing this?
I saw where the stop light switch can be a cause, but would the brake bar still work if that needs replaced?
Oh by the way I am in no way shape or form a mechanic so I need the "Jaguars For Dummies" version when telling me what to do! Thanks in advance!

 

It's likely that you have more than one issue here. You are right that the brake light switch also controls the high mounted brake light, but it does it through a different circuit that the main brake lights.

Before we start - I have to ask if you have checked the bulbs. It's easy to assume that they would not blow at the same time but they can and do.

The main brake lights are fed by the rear light control module. That's the ECU looking box in the rear fuse box (boot). It's about the size of an old VHS cassette.

The middle brake light is fed only via a relay which is also in the same fuse box referred to above.

Brake switch feed in to both the relay and the Light control module should be on a Purple/Blue wire and should have Ground when brake is pressed.

Output from the lamp module for brake lights is Green/Blue for RH and Green/Orange for left hand. These should go to 12v when brake is pressed.

If you have input ground but no output 12v when brake is pressed then the module has a problem.

 

Thanks for your reply. I have replaced all the bulbs and none are blown. I will go out and test those wires but upon researching I do suspect as well that its the module that has a problem. I found one on EBay for $49 that I'm going to order if in fact my investigating is correct.

 

No click when pressing brake while in park + no brake lights at that time, probably means brake light switch bad. Not uncommon. But there still might be a problem with the module as the very knowledgeable Brendan posted. Ground feed to the module will tell if brake light switch is grounding properly.

The high brake light bar relay has the red base.

We all would recommend systematic testing to be sure to rule out other causes, before buying the new module.

 

I remember a similar issue many years ago and might have been with an old 7 series BMW. Either way, both brake light bulbs had blown and the gear shift wouldn't move out of Park. This was because the onboard computer/ecu/ gizmo, detected hat the brake lights weren't coming on and so, incorrectly decided that the brake pedal wasn't being depressed and so, wouldn't allow the solenoid to operate in order to release the gear shift.

So, I imagine your two issues are definitely related, but sorry I can't offer any suggestions. Do keep us posted though and good luck.

 

Take a step backwards! Was this all ok before changing the alternator? All connections back on and no disturbed connections or broken earths around there?

The gearchange solenoid and brake switch are off the same control module. Check the fuses for that. Boot fusebox.

Steve

 

Before the Alternator issue the brake light problems were already present. I ordered a lamp control Module and brake light switch. Not sure what one is the problem but I guess better safe than sorry.