FactoryJaguarTech

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Join Date: Jan 2008
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ABS/DSC/TRACTION CONTROL: How it works!
Not sure if you guys/gals want to know things like this, but I was asked a question in the X350 section. So I thought I would post this response for all to have an idea how these systems work. If this post not in the right place, I am sure Admin will help out and put it in the right place.

Tractioncontrol works like this:

The anti-lock brake system (ABS) modulates brake pressure on each wheel independently to maintain vehicle stability during braking. The ABS continually monitors the rotational velocity of each wheel anytime the ignition switch is in the run position and determines if a tire is skidding when the brakes are applied. Only then does the ABS intervene to modulate the brake pressure to the skidding wheel. The modulation continues until the wheel rotates freely. The brake pressure is then restored and the modulate/restore cycle is repeated whenever skidding is detected. This cycle occurs at a rate of several times per second.

The ABS module is capable of detecting the following system conditions:

[ul][*]hydraulic valve failure[*]wheel speed sensor failure[*]ABS power relay short circuit[*]interconnect failures to the ABS sensors, power and ground to the ABS module[*]over/under voltage conditions [/ul]The ABS provides self-diagnostics and displays failure messages via the ABS indicator in the instrument cluster. Failure of the ABS module, for whatever reason, will not compromise the normal operation of the brake system.

The Dynamic Stability Control (DSC) system includes the:

[ul][*]anti-lock brake system.[*]yaw/lateral control.[*]full speed traction control. [/ul]The DSC system manages the braking system to enhance the driver control of the vehicle.

The DSC system continually monitors the steering wheel angle, master cylinder brake pressure, front and rear wheel speeds, vehicle yaw and lateral rate acceleration.

The yaw/lateral rate sensor supplies a signal to the DSC module, via a serial link, which monitors the vehicles rate of acceleration from its central axis in a sideways direction, and also the vehicles angular rotation around it's central axis.

The driver input parameters are continually monitored via the brake master cylinder dynamic stability control sensor, the brake pedal travel sensor and the steering wheel angle sensor.

DSC is enabled/disabled via the traction control ON/OFF switch.

Self-diagnosis of the DSC system is provided via the instrument cluster message centre.

Traction control is an additional function added to the ABS/DSC system. The vehicles driven wheels are continually monitored for wheel spin relative to the calculated reference speed and to each other. If wheel spin is detected, the traction control function intervenes independently of the driver, applying brake pressure to the slipping wheel and reducing the engine drive torque supply. Meanwhile, brake pressure is modulated by the traction control until traction is re-established. Traction control brake actuation is diminished above 40 km/h (25 mph). Above this speed traction control relies primarily on engine torque reduction.

Traction control is enabled/disabled via the traction control ON/OFF switch. When the switch is in the (OFF) position, the amber traction control warning lamp solidly illuminates within the instrument cluster message centre. The traction control is automatically activated when the ignition is switched on. Self-diagnosis of the tractioncontrolsystem is also provided via the instrument cluster message centre.

The traction control brake intervention is automatically disabled whenever the brakes exceed a temperature limit. The traction brake intervention will remain disabled until the brakes have cooled, irrespective of ignition switch position or ignition switch cycling.

I was searching the site looking for info on the DSC System fault because mine just started to display on the dash. Most replies to this issue seem to be the battery or cables connected to it. For the most part garage kept at all times, but driven daily. This past weekend had to keep the car outside and of course we get the Northeast storm with all the snow and water. The code just happened tonight so thinking better check the trunk in the morning to see if any water was able to get in. My question is this post by factory jag Tech, would this also apply to the S type specifically my year and should I also consider these issues listed? Thanks.

 

I read his post twice and I am unable to confirm everything he covered but what he did say made sense. A low battery, dirty sensor, poor connector connection (a common problem ), ABS module and a few other things are common. From my sources at Jaguar the 2000 S-Type had a few problems with poor connectors. I have a check list on my page that might give you direction. Note that my list is for a 99 XK8 so it will not be the same as your car.

Link Jaguar ABS Repair

 

Not sure about the 2000 car but the redesign (M45255 on - roughly 2003+) is very like that. Clarification: yes the cluster provides messages BUT they are sent from the ABS/DSC module. That module can store codes (there are unique ones for each wheel sensor, for module failure, and many other codes). Those codes can be read by a dealer-type OBD tool. Any ABS/DSC codes will NOT be seen by generic OBD tools.

edit: looking at the elec guide, the 2000 is the same structure

The common faults seem to be failing battery and dirt affecting the wheel "tone" ring and/or sensor -- for the latter, reading OBD with special tool should tell you which one (as well as telling you whether it's ANY of them lol)

 

Thanks for response. When you mean special tool, I am guessing I can use my own actron I purchased a while back which shows up nothing as far as any issues so either the dealer with a more up to date tool or maybe autozone and they have the tool to do the check? My battery is brand new (one year old) and everything looks very solid with it including the connections and no water in trunk so I fear it is your latter with the wheel tone ring or sensor.

 

You'll need specialist jag software such as Jag's IDS, WDS, (maybe NGS, SDD) or AutoEnginuity. No idea about the actron but if it doesn't have the jag stuff then it won't do.

AutoZone won't have jag stuff. Theirs is just generic.

 

boo

 

Just a follow up, after that day I posted the error code on the car, the next day and to date, I have not gotten the error message. I did check my battery cables and looked at the water levels in the battery and they looked ok but did add a little distilled water to bring it to right fill and since that time, have not had the code come up. I am a firm believer that water is the enemy of my car. If I keep it nice and dry and garaged, which was not the case for that week during our early snow storm, I seem have no or less issues.
I will do anything to keep water away. Is the code still showing Swoop22?

 

=(

 

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