Hello again, XKR fans- it is I, Arland Green, dauntless wannabe smart on Jags but on some things dumb as a clam.....

Since getting my engine work done and having had the 2005 model (an '04 from UK, I think called XK100 there and called one model year newer here) AJ159S 4.2 L V8 ported and relieved and polished, all was right and it was humming like the heaven a Jag can put you in when it is functioning as designed- and all of a sudden I made a 90 degree left turn and the DSC fault signal came on simultaneously as the engine acted like it was being starved for fuel- it was running but slowed at once to around 10 miles an hour and then just as suddenly it began functioning again normally. The Fields Jaguar tech had said I would need to run a few tanks of fuel through the car before I had it tested; the resultws were as they should be and my vanity 'My XKR' plate is again in good standing with the great state of Wisconsin. He said it would have to learn my driving characteristics again.

My question is, is a stall like that normal? I have new plugs, new wires, new coils, new valves and valve train, etc. as per my previous saga post. Mr. Moderator- please make sure that Graham sees this- he seems to be wiser than most and is most assuredly a virtual Grand Wizard on
jags compared to me. Thank you all for your interest and comment.
we are forecast for 7 inches of snow tomorrow or I would drive it to the dealer. I covet any and all answers.

 

DSC - my least favourite system. I much preferred the earlier setup on the 4.0 litre. What you describe sounds normal when the 4.2 is thrown around corners.

In fast cornering DSC will activate using a combination of restricted or reduced engine revs and application of braking to individual wheels to prevent the wheels locking or skidding. A very strange sensation which, depending on corner entry speed, can feel as if you've switched off the ignition!

The Message Centre has four relevant displays:

1. DSC : amber warning that DSC is operating
2. DSC SYSTEM ON : DSC switched ON
3. DSC SYSTEM OFF : DSC switched OFF using the console button
4. DSC SYSTEM FAULT : the system is disabled but the vehicle is safe to drive

Message (4) usually clears on the next restart unless there is a persistent fault in either ABS, Traction or Yaw Control.

The DSC system is ON by default when the engine is started and the DSC amber warning can either be constant or flashing as it kicks ON and OFF.

The Jaguar tech will have advised you to run a few tankfuls of fuel through before having it tested to ensure the OnBoard Diagnostic Tests had all been completed. The 'learning your driving characteristics' refers to the gear change points which adapt to an individual driver's style.

Graham

 

As Graham says the message 'DSC' simply means the system is operating.
Take your car out in the snow and slide it around a bit - you will experience the wonders of DSC.
It would actually be wonderful if it braked the rear wheel that was spinning on mud/snow which is when you really need it but no! you must be moving before it works.
If you are actually getting the 'DSC SYSTEM FAULT' message that's another matter.

 

Absolutely smashing answer!! I can't imagine a response more thorough and easier to understand than yours to my question, and what you described is exactly what I experienced, as you put it, as if I'd turned the ignition off. It also flashes, and turns itself off at the next engine start, all those things. It is just such a sickening feeling to be a siting duck obstacle after the turn, as traffic behind you flashes its lights and you brace for impact. Is there any programming or other mod or fix, or must I be very judicious in the g's I pull on a turn? Funny, but on the track it is fine- although there are no 90 degree turns on the track! Thank you again, Graham. You know, the 'Ask Jaguar' folks charge $35.00 for an answer like yours. If you'd like an easter ham, let me know.

 

Anything that disabled it would very likely cause a permanent DSC SYSTEM FAULT to appear in the Message Centre. Simplest way it to turn it OFF with the console switch after starting the engine. Unless switched ON again with the console switch, it will stay OFF until the next engine start. The warning message DSC SYSTEM OFF only displays for four seconds.

As Steve says, getting the 'DSC SYSTEM FAULT' message is another matter.

Graham

 

Posted at the same time as Graham so some duplication.
It sounds as if you're getting 'DSC SYSTEM FAULT'.
That is not 'normal'.
I know this sounds odd but check your battery.
A weak battery will produce that message. I get it when I start the car after two weeks in the garage and I know I need a new battery.
The other thing is to check the battery is firmly fixed down and the main earth connection is good.
Either of these could give a temporary loss of volts when you throw the car about.
The other possibility is an ABS problem.
It would be worth going to Autozone or wherever for a free code read.

 

Thank you. When the snow lifts (it is falling now, and you know what the Germans say- "Es schneit seinen Lauf"- okay, so it's regnet not schneit, who cares?) I can venture forth. We are actually colder than Moscow now with our lake we live on being frozen with 16 inches of ice and vehicles driving on it for ice fishermen.

Anyway, my point iis I won't be side shimmying to the ditch and dealer today in the snow, but will check Autozone and Batteries-R-Us to check the battery and its connections. The DSC System Fault warning language has only appeared on the three occasions I have turned sharply to the left at stop and go lights (traffic signals). It does not stay on, however, it goes off while I am driving. The eerie thing for me is this 'stall condition' of the throttle while the DSC is flashing just after the turn and about 5 or 6 seconds after. The maddening thing is it does not occur when I turn the same way with the same force to the right.

Thusly, methinks your loose battery idea could have merit. Also, the batteries when as cold as it gets here are lower in cranking power and voltage output- it was 9 degrees F here yesterday- that's - 12.7 C in the UK. Another way of looking at it is that if it warmed up here 22 degrees F (12.2 C) water would still freeze.

 

Your observation that this happens on LH turns but not RH turns got me thinking further about the Yaw Control mechanism. The issue could well simply be due to a loose connection as Steve has suggested or it could be an imbalance in the sensing setup.

The Anti-Lock control - Stability Assist system continually monitors:
1. master cylinder brake pressure
2. front and rear wheel speeds
3. vehicle yaw and acceleration
4. steering wheel angle

The yaw rate sensor and accelerometer supplies a signal to the ABS system module through a serial link monitoring the vehicle's rate of acceleration from its central axis in a sideways direction and also the vehicle's angular rotation around it's central axis.

Driver input is continually monitored through:
1. brake master cylinder pressure transducer
2. brake pedal travel switch
3. steering wheel rotation sensor

The part of this I hadn't really picked upon before is the 'steering wheel rotation sensor'.

If your fault isn't eliminated by attention to the battery connections, I'll do some further checking to find out where this steering wheel rotation sensor is and how it operates.

Graham

 

Steering wheel rotation sensor's a new one to me - I haven't seen it in the JTIS.
I wonder where it is ?

 

It's amazing to me how fast you guys can make me feel dumb! 0-Ignorant in 3.2 seconds. Thanks for the further lesson. This DSC is really quite a complex mechanism.

 

Too complicated.

Almost makes me long for the days when I only had a GO pedal, a STOP pedal and a Steering Wheel with nothing else interfering. An armful of opposite lock took care of most other things!

Graham

 

And that third pedal and thingy sticking out of the floor.

 

You are right as rain, Steve- Graham you mentioned it too- it has been definitely proven to be3 the YAW control, specifically the accelerometer. I will have my JAG back in time for its reupholstery appointment on the 13th.

Odd thing is that it is sunny and in the 80's F all of a sudden after taking the JAG to the dealer!!! Saw a radiance red XJ8 Van Den Plas there though, with a license plate that said 'JUNGL CAT'. Thanks to all you educators- made me sound smarter to the techs.