Now that my ABS unit is rebuilt and working properly I got to actually looking at the system mesages that come on during the current snowy period here in Chicago.

When it's slippery and I accelerate enough to break traction I get a yellow warning and "ASC" message. (Automatic Stability Control?) When braking I feel the ABS pulses, but I don't get any sort of message.

When the ABS unit was broken I used to get a TRAC warning a hundred times a day, but now - nothing ever. This is certainly some sort of traction function - but what exactly is it? How come the TRAC message never comes up in all this slippery weather? I've tried turning it off/on from the dash - with no perceptable difference in anything.

Thanks!

 

Spurlee,

Neither my 2000 XK8L nor 2001 XK8 4.0 had Automatic Stability Control fitted. My present 2005 XK8 4.2-S does have it.

I'd expect your 2000 XK8 to have ABS (Antilock Braking System) and TRAC (Traction Control). If it does have Automatic Stability Control as well, feel free to shoot me down in flames.

Traction Control intervenes to prevent wheel spin if this is detected by the wheel speed sensors. When this happens, engine torque is controlled and individual wheel braking is applied.

TRAC is on by default when the engine is started. It can be switched off by pressing the TRAC button on the centre console switchpack. Engaging Cruise Control also automatically disengages it. When the system is activated, the amber warning light flashes. If it malfunctions, the message 'Traction Control Fail' is displayed.

ABS automatically activates if the pedal pressure exceeds tyre adhesion to prevent wheel lock. You'll feel the pulsing in the pedal when this happens. If there's a fault with the ABS, the amber warning light is illuminated.

The amber ASC message you're seeing is to advise when Traction Control is operating - it's not a fault.

Graham

 

ASC, by Jag's standards (at least in my '98 XK8), is merely a throttle/power reduction. ASC by most/many other OEMs employs accelerometers, steering input sensors, brake pressure sensors, etc. and can vary throttle, total brake as well as individual brake(s), torque split (AWD models), etc. to help you not fly off the road when doing something stupid. Another way of helping people not pay attention to the task at hand...

 

Beav,

I'm not a great fan of these 'driver enhancements' either.

Still haven't worked out just what benefit Automatic Stability Control is supposed to give me. Perhaps I need to floor the throttle and apply maximum steering lock at 70 mph to find out...

Graham

 

Thanks everyone!

 

The Jag ASC only reduces throttle/power. Steering input, etc. is not oster of the equation. Basically it is traction control without using the brakes.

 

Right-o!! Good analogy.

Spurlee,

ASC pops up on the message center anytime the system starts to counter a wheel slippage. It does that because sometimes, especially at higher speeds, it is hard to detect that slippage by the seat of your pants. That way you know a wheel is loose.

The other messages, TRACS for instance, only show up if a failure of some sort is detected, as when your module had failed.

Hope that helps.

Cheers,

 

AH HA! My module was troublesome for quite some time - so I was used to seeing the TRACS message. I interpreted TRACS and ASC messages as representing two separate traction maintenance features.

Now I get it. Thanks!