I'm not sure if it's called limp mode(traction control, abs, seatbelt, gearbox failure and check engine light as well as the radio doesn't turn on and sunroof doesn't open or close) but that's what it feels like.

A few months ago I changed my brake pads and of course used my jack in the trunk. Some how I trigured something in the trunk that put my car in limp mode once I started it back up. I hadn't had any problems with it since then until recently. Now every once in a while when we go to start it the battery almost seems dead(only about 6 months old) but then it starts without a problem but is in limp mode.

I guess my question is are there any wires or anything back there that could trigger this? My battery cables are tight and I've looked for loose wires but I've found nothing.

 

All the faults together point to battery failure. You say you replaced the battery 6 months ago. Now a couple questions.

What year and engine? (hint: update your signature so we don't have to keep asking)

Why did you replace your battery?

With very limited knowledge of your car I'm going to guess at two things... Both common to some cars.

Water intrusion into the trunk causing a short or two...

Faulty ignition switch causing the car to "stay awake" draining the battery..

 

Sorry about that. I'll update my sig right after this. My Jag is an 03 with 115k on it. I replaced the battery because the old one died.

I haven't seen any water in the trunk but to be honest I don't look in the trunk very often.

I've started and driven the car three times today. Each time I started it everything had been reset and I was back in limp mode.

I don't think it's the ignition switch as you asked because of it being reset each time.

How would I check for a short? I'm thinking that's what it might be because of the way it started. I must have hit something but not hard and it killed the connection which seems to be getting weaker and weaker.

 

My limp modes were caused by the battery. It had sufficient voltage to start the car, but the amps were down which sent false signals to the ECU. One new battery and no more problems.

 

The water will be inside the spare tire well. I don't think anything is shorting out at this point, unless you are getting water in where the spare is. But then you would be able to see/find burnt fuses.

If you do a search on "battery drain" or ignition switch" you will find other threads that deal with the issue...

What happens, in a nutshell, is individual modules shut down in stages in these cars. A faulty ignition switch can actually seem like it "works" just fine but doesn't allow the car to "sleep". If all the modules don't shut down, there is a constant drain on the battery that will in turn trigger all kinds of fault codes.

 

One of the most common causes of S types going into limp mode with multiple failure warnings (no DSC, ABS, Park Brake etc) is the parkbrake harness (Loom) that sits above the back axle.

This chafes through and when the conductors come into contact with the metal of the body, shorts out and causes the main EMS module to go bananas.

It is a simple job to locate the loom, insulate the worn wires and then tie it back out of the way of further harm.

Some unscrupulous garages carry out this repair and then charge hundreds of pounds (or dollars) for replacing Throttle bodies uneccessarily.

 

I don't think that has ever been reported before. So, it would appear to be incredibly rare...

 

I agree. This has not been reported before so I don't think the wiring is the problem.
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Easy to check and significantly cheaper than replacing the TPS

 

But hardly anyone DOES replace "the" (*) TPS.

(*) Er... do you actually mean TPS - which of the two? Or something else but you've called it TPS?

I'm dying to know your evidence. It's not on here, is it?

 

Load test the new battery - also, check to ensure the battery is the correct one specified for your vehicle. (CCA, etc) - I had an incorrect Interstate battery installed professionally - clearly, this was the wrong battery and my Jag essentially fried this battery and rendered it useless in less than a year.

Just sharing my $0.02