I have a 2004 XJ8 and would randomly get the code when starting or well driving engine system fault, dsc not available and park brake fault and of course get put in limp home mode which makes the car worthless. The cause of this issue is not the parking brake or traction control. It is a dirty throttle body, do not be fooled and buy a new one. Simply go to the auto parts store buy throttle body cleaner for a couple bucks. Disconnect the battery Remove the plastic engine cover and the black tube going to the throttle body. Get a rag and the cleaner and scrub the inside of the throttle body top bottom and both sides of the flap until it is shiny and clean. (30 – 40 min of scrubbing for mine) than reassemble and drive the car. You will need to drive about 20 miles before the computer adjusts to your driving habit. Do not buy another throttle body it is a complete waist. Any questions email me ford289ci@aol.com

 

This fault is generated by sporadic or spurious signals from the Denso throttle position sensor. It can either be a failing sensor or a harness problem. Cleaning the throttle plate may not be a long term fix....sorry.

 

How much does a throttle body cost anyway? $800 or something?

 

Well my car was doing it every time I drove it and once I cleaned it it has been a year and a half and it has not don't it once again so I think this problem is solved

 

Apparently the throttle body is coated on the inside with a type of lacquer?

does anyone know the purpose of this and why you have to be careful with

which cleaner you use.Presumably petrol is ok?

thanks in advance

 

Thanks for sharing your experience. Certainly it's something to try before you go replacing the throttle body!

 

Thats what I am saying before you drop 2000 on a throttle body or 800 for a rebuilt one you might as well try cleaner yours. I think there is a place in orange,ca that sells rebuilt ones with a warranty for $600

 

Where is the throttle body on a SuperV8? I could not find it.

 

What are the codes you are getting? If you do not have them you need to get them. Write them down and post them and we will see what you have going on.

 

Ran diagonistics:

P2135 TPS/Pedal position/Electrical fault

P1111

 

I had the same problem and solved it by cleaning the mass airflow sensor and throttle body - that solved the problem for a while (See previous posts). On 11/8/11 the problem reappeared and I finally took the car to an exotic car expert (over 30 years working on jags, ferarri, lambo, astins, etc) and he informed me that the "engine fault, dsc not available and parking brake fault" issue is common and has nothing to do with the mass airflow or throttle body. I was explained the following: there is a separate diagnostic computer system that monitors emissions (the system is contained in the same wiring harness as the other wirings). This system sends out a signal to the engine then to the transmission then to the wheels. The purpose is to make sure that those items are performing with specified parameters as set by emission standards. Typically what happens is if the signal does not make the proper loop, the system starts shutting down various items (i.e thus check engine light, DSC not available, parking brake fault, etc) and places the car in limp mode. The solution is to pull the codes and to test each module in the system to find which module is causing the problem (i.e. not sending the signal so as to complete the loop). The system has been installed on a lot of cars (not just jags) for the past 10 years. Unfortunately the problem has been occuring mostly in jaguars. I hope this helps. I will provide an update once I get my 2004 S-Type back (I just took it to the shop yesterday 11/9/11 for the "engine fault, DSC Not Available and Parking Brake Fault)
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In my case it turned out to be a bad sensor manufactured by Toyota...

 

IT'S P0121 WEATHER AGAIN.

When Jag made up the wiring for Jags like the X350 models and others, they forgot to seal against moisture.

On the side on the throttle body is a 4 wire connector that is at the throttle position sensor. Get a little wet in there and bingo, you get a limp home mode along with the warnings the the DSC and Park Brake have failed.

Press the lock tab in on the plug and plug the plug loose. Spray the 4 pins of the sensor and the inside of the plug with something like WD-40. Plug and unplug it several times to clean the contacts. In most cases that will fix it and away you go. Later seal up that connection. The wires at the plug have a sponge looking seal which doesn't seem to work.

 

Man, I'm telling you, just being a fly on the wall around here is kind of like buying insurance. I'm armed with so much information, stored for the "what-ifs" that will eventually come. Great stuff.

 

My 2005 XJ8L w/ 80k miles has finally had it. I've had this problem for 1.5 years and 30k miles. It would go into limp mode for a few minutes every few months; I cleaned the connections and made sure they were tight and it was fixed. As of this past weekend, the car goes into limp mode within 1 minute of starting. I am starting to think I will have to break down and buy a throttle body and install it.

Is it worth buying a new one from a dealer or online parts shop for $847 with a warranty or go with a rebuilt one? What would be the best value for my money?

 

rycymru:
I get the same thing every so often, usually after a wet time. I am the original owner of a 2004 XJ8 with less than 40,000 miles on it. I believe that once the contacts at the throttle body get the *&^%, we have to unplug it and do the plug, unplug ritual to keep it clean. Early this year when the P0121's were popping up, some of the bunch here were changing to gold contacts.

 

The problem is that it isn't every now and then anymore. Its every time i start the car. I have been trying to fiddle with the TPS plug, but it doesn't fix the problem like it used to. The code that pops up is p2135, throttle position sensor. I found a used one for $450 with a 6 month warranty and a new one is $880 with a 12 month warranty.

 

I'm a newbie to Jags and have never monkeyed with the TB or TPS of my car or any other Jag. But I know that if I were getting those codes, I would remove and completely clean and dry the TB and TPS and re-install them before I replaced either. My .02.

 

I spent all weekend cleaning the throttle body and the sensor, but no luck. I noticed that the lights come on when the engine goes below 1k rpm everytime i start the car.

Last night i installed a new throttle body for $898 and it took around 30-45 minutes. The car runs fine now, no lights or problems. I've only done a few miles around town, but i will take it on a small trip tonight and make sure it's fixed.

I've had this problem for 1.5 years, but it only happened for a few minutes every few months. It seems that last week the sensor finally died and i had to replace the whole throttle body.

 

I ve had the same issues last May 2011, and unfortunately i needed to replace the complete throttle body.

parts and labor $1200.00

ouch!