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  #1  
Old 01-13-2008, 05:42 PM
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Default 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.

Traction control 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 traction control system 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.

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Old 01-13-2008, 07:05 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

FJT, since i got my XK8 in april of 07, the message center has shown a DSC system failure/fault (can't remember exactly) twice, under no specificdriving condition. I was just tooling along in town, and the error came up. I caught a cell phone picture each time, but it is neither frequent, nor predictable. any reason to suspect anything serious, or could it have been the brake temp that could have temporarily disabled the entire DSC system? Just want to know if I should be worried or not.

Side note, you're spewing a ton of helpul information on here lately, kinda wonder if you have had the last couple weeks off work or something...and am curuoius as to how you have so much time to contribute to the tech issues in the forum..?? Do you ever sleep? [sm=sleeping.gif]
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Old 01-13-2008, 07:15 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Great info!!!! By the way, do you work at a dealer or an independent shop?
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Old 01-13-2008, 08:30 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Work at a dealer.
The info I give out is because I care enough to do so. If you don't see me reply within 48 hours, something has gone terribly wrong..lol
I work everyday except Sunday. Only takes a few minutes to type a message so I don't mind. And yes I sleep normally while I am scanning the cars. Gives me a few winks.

What year is your XK8 H20Boy? If the light comes on intermittently probably needs a module. Need the code from it. It will be stored even if light not on. There is 2 connectors on ABS module. Left fender by washer bottle filler. The upper is main harness, the lower is a 2 pin connector. Disconnect that and take an ohm readin. If over 4 ohms it needs a pump. If under, needs module. Sometimes needs both because one shorts out the other. Anyway, this is assuming you get C1095 code from module.
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Old 01-13-2008, 09:40 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Hey FJT, it's an '03, and I will see if Autozone or O'reily's can pull a code before i try to test the module. Strangely, I had the LF wheel off tonight to clean up the brake caliper, and if i had gotten this note before finishing, I could have taken an ohm reading. Lets see what code comes up, and you can direct me from there, k?


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Old 01-14-2008, 06:56 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

In regards to DSC would failure of the booster cause loss of the DSC or would it lean more towards a sensor
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Old 01-14-2008, 06:59 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

It depends on the vehicle. For example, the S-type and X as well as XJ 2004+ have a pedal travel sensor in the booster so it would cause dsc failure if that sensor went bad. If no sensor in booster, then shouldnt affect DSC system.
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Old 01-14-2008, 07:26 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Autozone tried to pull a code from my XK, and figures...he couldn't. it kept reading 'connection error', which means he couldn't even get it to talk with the car. Any tips for this guy, or some other place I could try? i'm going to go take an ohm reading on the ABS module...so let know you in a bit what it says.


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Old 01-14-2008, 08:06 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Is this the 2-pin connecter you were referring to? (SEE red arrow)

Click the image to open in full size.


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Old 01-14-2008, 08:51 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

yes. Disconnect the main harness first then the one below it. Make sure you have good connection when you ohm it.
Before you go thinking about changing parts, get the codes.
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Old 01-14-2008, 10:03 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

its a 2003 s type
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Old 01-15-2008, 04:46 AM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

In that case Dyno, a booster problem could cause a dsc fault.
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Old 01-24-2008, 10:16 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

When you say the brake booster do you mean the vacum brake booster behind the master cylinder?
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Old 01-24-2008, 10:23 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Yes the vacuum booster. It has the brake master cylinder bolted to it. The parts in there arent available seperately from dealer so we replace whole booster for problems.
DO you have a fault? Do you have codes?
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Old 01-25-2008, 12:12 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

The dealer only told me that the cause of the DSC light being on the dash is caused by the booster being faulty, they said it will cost $1400 to replace it. First the torque convertor at $3000 now this starting to think I have lemon on my hands. Total quote for repairs is $5100 canadian taxes in.
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Old 01-25-2008, 06:15 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Do you have any Select edition or extended warranty?
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Old 01-26-2008, 12:05 AM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Got an aftermarket warrenty package when I boughtthe car, but they only cover up to $2g's a claim. Is that a fair price for the brake booster seems awfully expensive for just a vaccum booster behind the master cylinder.
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Old 01-28-2008, 06:27 AM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

The brake booster for an S-Type between vin m45255 and M81056 is part number xr8-43545 and retails @ $717.55 USD.
Labour is approx 2 hours. So about $1000.00 or so. I dont know exchange rates so if your in Canada adjust accordingly.
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Old 02-11-2008, 12:02 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

Quote:
ORIGINAL: FactoryJaguarTech

Work at a dealer.
The info I give out is because I care enough to do so. If you don't see me reply within 48 hours, something has gone terribly wrong..lol
I work everyday except Sunday. Only takes a few minutes to type a message so I don't mind. And yes I sleep normally while I am scanning the cars. Gives me a few winks.

What year is your XK8 H20Boy? If the light comes on intermittently probably needs a module. Need the code from it. It will be stored even if light not on. There is 2 connectors on ABS module. Left fender by washer bottle filler. The upper is main harness, the lower is a 2 pin connector. Disconnect that and take an ohm readin. If over 4 ohms it needs a pump. If under, needs module. Sometimes needs both because one shorts out the other. Anyway, this is assuming you get C1095 code from module.
Hi FactoryJaguarTech,
Great info you post...............I have a 97 XK8 with same problem. I have C1095 fault diagnosed by dealer and have not put a meter on it yet. I have cleaned terminals with switch cleaner. The module is ATE type part number LJA221OBH............Dealer wants $1995 for part, I can getmine repairedfor $140............should I just buy it. Is the car driveable while the module is off the car please?
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Old 02-11-2008, 01:22 PM
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Default RE: ABS/DSC/TRACTION CONTROL: How it works!

C1095 code will be either module or pump. Meter will reveal all.
I would advise against driving it with the module out. Let us know how the rebuilt works. We have not had good luck with rebuilt abs modules.
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Old 02-11-2008, 01:22 PM
 
 
 
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05, braking, control, controls, dsc, failure, fault, jaguar, relay, stuff, system, traction, type, works, xk8



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