ABS light on.... when you need it most
 

Recently I had to stamp hard on the brakes and was amazed to find the ABS light decided to come on at that moment, and remove the ABS function. Long black skid marks and lots of tire smoke appeared to confirm I didn't have ABS (although I stopped very quickly as the road was dry)

The symptom is repeatable, ie hard stamp on the pedal, at idle even, will cause the ABS light to come on.

'92 V12 XJS US spec..... not even sure what kind of brakes I have on it (I usually don't mess with brakes or fuel things)

I could use clever words like TEVES and accumulator, but the truth is I have no clue so I will ask the experts to guide me as usual

Thanks in advance

Hi Sarc,


Like you I am having ALBS issues but in my case the light is on all the time.


In your case I suggest you first check the ALBS 30 AMP fuse and if ok then see p 109 of the Jag XJS service manual. Seems like for your symptoms the things to check are:


1. wheel sensors, condition and wiring
2. brake disc damage
3. wheel bearing play


Others will know more.
Good luck,
LeeP

Hi Sarc

There are generally a couple of reasons for the ABS light to come on and more that likely its the Wheel Speed Sensors, which will probably just need cleaning. (or maybe replacing)

It would only take one of these to get gummed up with 'crud' for the ABS to detect a problem and then the ABS light will come on.

The Sensor takes a reading from a gear wheel on the hub and these can be quite prone to getting dirty.

One of the other reasons for the ABS light to come on, can be caused by uneven Braking, so check to see if the Pads are wearing evenly.

If the Pads are wearing unevenly, then it could be a Sticking Calliper.

In the event it is none of these things, then it could be something more serious like unevenly worn Rotors or even a cracked or worn wheel bearing or a cracked hub.

If you are not up to having a go and fixing this yourself, The ABS stores a Fault Code, which can be read with Diagnostic Equipment at your Garage/Shop.

Which should be able to 'pin point' the problem.

Sarc,

Many of the causes of the ABS light coming on relate to the continuity electrical problems rather than faults within the hydraulic system.

Look through the Service Manual as it explains the combination of ABS and Brake Warning lights. It also explains how to do the 32 diagnostic tests which test the electrical integrity and continuity circuits.

Good luck

Paul

Thanks for all the feedback. I haven't done much work to the brakes on the car so this may be the time to learn about them and hopefully also track down the fault.

Are the brakes on my 92 facelift car the same as earlier 90 and 91 cars?

If so, what type of system is it referred to as ? (this may help me searching the forums)

The Teves Mk III ABS system was used until early '95.

IIRC, the ABS does a full system check at start up and once you drive above 10mph, so if any component isn't working it will light the ABS light on the dash.

It appears yours is passing the system check, but some part of the system is failing ONLY under hard braking. Off the top of my head, I would suspect a pressure problem or leak. The black bulb-like pressure reservoir (I believe it's called the "accumulator") can leak or fail. Just thinking out loud, so don't focus solely on that.

If you haven't already, download the "Book" and find the section on the ABS brakes, it's a really good explanation and also highlights some errors in the Workshop Manual. There is also some tests listed there you should try.

I doubt if its an Accumulator (Black Tennis Ball on top of Pump) problem, as if this were to lose pressure, you would probably have to stand on the Brakes to get the Car to pull up.

As with a serious loss of pressure, the rear brakes wouldn't be working and you would be left with Braking on the Front Wheels 'Only' as this is a built in failsafe in order to Stop the Car.

The Fact that you left 'Skid Marks' seems to indicate, that it wasn't a loss of Pressure in the Accumulator.

More likely to be a malfunction on one of the Wheel Sensors caused by a build up of 'crud' on the gear ring from which it takes its reading.

Check for uneven wear on the Pads and the Rotors, which would be quite easy for you to do yourself, before you start to throw any money at it by taking it to a Garage/Shop.

While you've got the Wheels off, check for a loose or worn bearing.

When checking for a Stuck Calliper, do NOT be tempted to lever the Brake Pads back with a screw driver, unless the bleed nipples are open and the brake hoses are clamped off.

If Fluid is forced the wrong way up the System, any microscopic particles of dirt in the Brake Fluid (which you wouldn't even be able to see) can literally wreak havoc with the 'Teves' Master Cylinder/Actuator.

Rendering it inoperative, for which Spare Parts are virtually Non Existent.

I don't think that could be it, because a malfunction or wiring fault from one of the Wheel Sensors will turn on the ABS light once you go above a certain mph. It would NOT require hard braking to show as a fault.

I believe there is a way to read the fault code from the ABS ECU in the boot, but I think it only stores one fault code at time. You could check the fault, clear it, rerun the test of hard braking, and recheck the fault code.

EDIT - I should add that I hesitate to correct you orangeblossom because I can tell from your posts that you know a great deal more than I do!

ABS codes and assistance
 

Jaguar ABS. This is a link to the rear (boot) test plug to identify where the ABS problem may be. I used a paper clip to make the connection. Also see the thread (XJ40) 1986-1994, dated 6-4-2012 from Bdshultz "another xj6 newbie with ABS codes". this thread will be of great assistance to your dilemma.

Mine has done it... hard stab of the brakes, car pulled violently to one side (don't remember which). It's a nasty feeling which doesn't inspire much confidence in the car. Felt like it was trying to kill me.

Flint Ironstag,

I think your problem is quite different to this thread of Sarc's. He has lost the ABS function across the system.

Your symptoms sound much more like jamming of one of the solenoid valves in the ABS valve block. There are a number of threads on here describing those symptoms and the resolution.

Cheers

Paul

The ONLY way to find this problem is to start at one end of the system and systematically work through.

I would start by pulling the sensors out and check for debris in the reluctor. If you have a damaged sensor or metal in the reluctor (not a complete failure) the system will not find this until you hit the brakes. I would look at the front first as the front is not dynamic until ABS function is required.

There are 3 pressure switches in the pump, 2 NC and one NO the NO one operates and is closed if pressure fall below a pre-determined level turing on the ABS light.