Hi all sorry my first post is a request for help but you know... thats kinda how these things go.

I have a 1989 XJR-S 5.3, after a long and convoluted process I'm in a position where my ABS light has come on and I dont know why. The brakes themselves work and can lock the wheels/skid the car if prodded too hard. The car brakes in a straight line and best as I can tell is using all four wheels to brake, so mechanically they seem fine.

I've already done a forum search and tried to diagnose the problem from the information on previous posts but I've hit a bit of a brickwall...

Things I've tried :-

• So I'm aware that the car needs to be moving above 19mph for the system to reassess and reset it's light, I've done that after each of the below.
• Flushed and bled the fluid
• New front calipers/disc/pads
• I've jumped the ECU diagnostic port and received error code 21 through the dash light. I believe this is telling me I have a general electrical circuit problem.
• I've found a post by 540itouring that said about testing certain pins on the ECU (35 , 16 , 33 , 17 , 34 , 15). I do have these result but I'm fairly sure the wiring on my car is different because the pin 33 on mine isnt used - i.e. is one of several pin holes without the metal connectors in the plug itself. Given that it would never read the low resistance he's looking for, his post mentioned the circuit for a 91 car so I'm assuming the facelift wired up the pins differently to a pre-facelift 89.
• 540iTouring then says "Then check pin 11 to ground on the car metal (low) . Then ground on car metal to pin 18 of abs ecu plug " both of these did get the low resistance, but as per above I'm not 100% sure I'm testing the same part of the circuit he's looking for.
• I've tested the resistance from the two pin plug on the reservoir "main solenoid" and got the expected 5.x ohms.
• I've tested the resistance from each pin on the valve block and got the expected resistance from each and out and in pot.
• On the valve block I've also put 12v across pin7 and the each valve in turn, got a solid "click" from each pot.
• I've replaced the accumulator sphere as I was initially getting none stop pump noise, I now get about 10secs of pump noise and then again after a couple of goes on the brakes.
• I had a problem removing one caliper as a bolt snapped, this resulted in several attempts to fix it including heat treating it and eventually completely disassembling the hub - speed sensor and all. If I had a dodgy wheel sensor I'd put money in it being that wheel but the error code I'm seeing doesn't appear to suggest it's wheels speed sensor - there is a separate code for that - could I be missing something

So all in all I'm at a bit of a loss. I'm fairly convinced it's an electrical issue as the brakes themselves seem to work and we appear to be failing the initial self-test rather than seeing a problem when moving.

I'm wondering if anyone could suggest the next step in diagnosis. I've actually tried to just pay someone else to deal with it but no-one seems to want the work. I've called three jaguar specialist and they've all be very polite and helpful but have turned away the work and sent me onto the next person. I guess the ABS system is so notoriously hard to deal with no one wants to take the risk of spending Łks of my money to not have fixed the problem. Which I totally get, but its left me in situation where if the car is ever going to get back on the road it's down to me to fix.

I'm wondering about disconnecting the wheel sensor I think maybe dodgy but I'm not sure what I'd expect to happen in normal circumstance. Would the self test pass because it sees no error, would it fail but with a different code... should I be leaving it disconnected all together or should I be jumping the circuit to make the ABS-ECU think it's still there and A-Ok...

If there is a better next step please feel free to suggest it ?

I can see a few members that seem to have a fair bit of experience with the ABS system but I think I'm seeing that they've not been active for a while is there anyway to give them a prod ? Is that poor form ? (orangeblossom, djinaustin, 540iTouring)

Any assistance greatly appreciated...


Thanks in advance

 

Welcome to the forum.

Stop by our new members area when you get a moment ==> New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum

 

cityslang,

Before changing anything, I would start by running through the 32 diagnostic test in the workshop manual which will verify, or otherwise, all the electrical integrity signals and circuits, including the wheel sensor circuits. You can then see where to go next.

Good luck

Paul

 

Hi Paul, the 32 tests were my very next port of call.i have the ROM on CD but it wasn't loading on my PC. After I posted I found a PDF of the section I needed.

So I started at the bottom becuase I had a sneaky feeling that pressure switch might be the issue. Obviously I was totally wrong.

So I started at the beginning and guess what ? Failed the first test, with ignition on the abs-ecu isnt getting 12v across pin 1+2 ... I've tested pin one and it has decent continuity with the battery earth. So I guess the of ignition switch isn't sending through 12v to the ECU.

I've tested the fuse in the passenger side that says abs-ecu, it's getting 12v even with ignition off and seems to have good continuity. I've had a look at the back of the ignition switch and there doesn't seem to be anything hugely amiss.

Are there any known failure points between the ignition and the ECU ?

 

Hi Cityslang

Your problem is showing Classic Signs of not Bleeding the Low Pressure side of the Brakes, especially as you have replaced the 'Black Tennis Ball' 'Thingy'

So the Question you may be asking, is how come the Brakes are working?

The reason being there is a built in 'fail safe' whereby if part of the system should fail, then you would still have braking on the Front Wheels.

Which could easily have you believing that all the Brakes are working, when they are not.

Under those circumstances, the ABS light will remain 'ON' to Alert you to a fault.

So if you haven't yet Bled the Low Pressure side, this should very hopefully solve your problem.

Its a really messy job and you will have Brake Fluid, flooding all over the place, where you won't need me to tell you, that if it gets on the Paintwork it will strip the Paint off in an instant.

Including inside the Engine Bay.

So best to spray Spray Grease over any exposed Surfaces in the Engine Bay, that may come into contact with Brake Fluid and Pack loads of Rag and Bath Towels, all round the Accumulator 'Black Ball' 'Thingy'

The Accumulator Screws into the Pump and on the end of the Pump you will see a hard plastic Pipe which has been formed at an Angle.

Holding this angled Pipe in place is a 'Tiny little pin' with a very small ring on the end of it.

So before you Start de-pressurise the System by giving it 20 pumps on the Brake Pedal with the ignition OFF.

The next job is to pull out the little pin (which should be very easy) but Don't Lose the Pin!

Then you have to Pull out this Hard Plastic Angled Piece of Pipe.

This is not as easy as it looks, as it won't want to come out, as its held in place with an 'O' ring.

So you will need to protect it with a Piece of Rag and very gently grip it with some 'Mole Grips' as near to the Straight part of the Pipe as you can.

Then you need to Twist it and Jiggle it, as if you were a Dentist pulling out a Tooth.

But be very, very, Careful you don't break it as you won't be able to buy another one, very easily if at all.

Also when you do this, throw a big Towel over the Pump, as if there is any Pressure left you will have Brake Fluid, Squirting everywhere! (so be aware that can happen)

Also make sure that you have a 'mate' who knows what they are doing, to keep the reservoir 'Topped Up' while you do this.

As soon as you pull the Plastic Pipe out of the Pump, Brake Fluid will start flooding out.

So as soon as you see Clear Brake Fluid run, then put the Plastic Tube back in the Pump and replace the 'Little Pin'

Then before you go any further get soapy water and a Sponge and Sluice anything down, that may have come into contact with Brake Fluid.

Then Bleed the Brakes all over again using the 'Teves' Method and not the Jaguar Method.

PTJS (Paul) is a bit of an Expert on this, so hopefully he will jump in.

When you Bleed the Brakes, open the Bleed Nipples and Clamp the Brake Hoses, as if you Force Brake Fluid the wrong way up the System, towards the ABS, this can very easily cause some Major Damage to the Valves inside the Valve Block, for which there are no spares.



As you can see I made a Shute out of Tin Foil, to divert any Spilt Fluid into a Container placed under the Car.

Also pull any Brake Fluid Soaked Rags, out from Under the Car and Not over the Bodywork, in case you get any drips.



Hopefully This will help to Solve your problem.

OB.

 

Hi Cityslang,


Pin 1 is the earth for the ABS ECU and it sounds as though you are getting this. Pin 2 should be 12V supply with ignition on. You should also get 12v to Pin 19 when engine is cranking - this is also another check on ignition switch.


Lots of places where the circuit might be broken from ignition switch to Pin 2 of ECU. You will just have to trace methodically back.


I'm presuming that you have all the various wiring diagrams of the ABS system. If not ping me a PM with an email and I will forward as I gathered various ABS diagrams in sorting out my own ABS problem which took 6 months so good luck.


Cheers,


LeeP

 

Hi guys, thanks for the responses. I actually feel like I'm getting somewhere with this for the first time in 18months

OrangeBlossom
I have bled the low pressure side of the system since fitting the accumulator. I followed the guide at Jaguar XJS Restoration : How to bleed Jaguar XJS teves ABS - which looks to have more or less the same steps as your post. However, I did that when I'd only bled the high side using what I'd call a traditional method. Although I got them firm, over the next few days they totally lost pressure. I have since done some reading established that I should have done it the teves way, so I did and got proper brake pressure that stayed. I was minded to go back and try this again just to be on the safe side.

I am curious thou, would air in those cause the ABS-ECU to not get 12V. I assumed if it had a pressure problem, then the ABS-ECU would get 12V and an error signal and refuse to work, rather than something else refusing to give the ECU 12V. Also the combined pressure switch seems to be giving the ECU the okay according to test 32 - like I say I skipped to the end thinking it was a pressure switch issue - if there was an air in the lines problem that pressure switch would be reporting issue would it not ?

Don't get me wrong I'm not trying to poo-poo your suggestion, like i say I probably am going to go back and revisit it, I just wanted to make sure my way of thinking about the problem isn't missing something vital to design. I was a bit surprised when the ABS light came on with the ABS-ECU removed, I expected to see nothing there.

leep123
I've got some wiring diagrams, I reckon if the ABS loom was completely out of the car I could tell you what each component was, however when it's in the car and all bundled together with the numerous other systems I do struggle to see the wood for the trees. When I pulled the car up it did work perfectly, I'd be surprised if wiring has suddenly stopped working so I'm reasoning it's more likely a connection at a component than the wiring run itself.

I'm wondering about an additonal fuse or something other than the one in the dash I've already tested. While the car was in the garage before all this happened I had it running and the battery lead came off when I pulled something else out of the boot. The engine carried on running, so I stupidly just grabbed the lead and re-attached it. That seems to have caused a surge that's taken out my stereo - least of my worries at the mo - but it could have easily also done for any inline fuses the ABS-ECU has between it and the ignition. I've check the main fuse and that seems fine.

Also I'm somewhat confused, if the ECU isn't getting any power on pin#2 I'm assuming the ECU effectively has "no power". If that's the case, how is the diagnostic light returning error codes ?

Once again thanks for all you assistance, I do feel like I'm closing in on the problem...


Simon

 

Hi Simon

I am not into Auto Electrics, so anything on that side would be better answered by someone like 'Leep' who unlike me, really seems to have nailed the 'inner workings' of the Electrical Side of the ABS.

While I was reading about your problem with the ABS, the very first thing that came into my head was the 'Fuse' which should be the first thing that needs to be checked, as sometimes the Solution can be as simple as that.

But since you said you had checked the Fuse, I totally discounted this as being part of the problem and since all the Valves were 'Clicking' and you were getting good readings, came to the Conclusion (The wrong one in this case) that your problem must be on the Low Pressure side.

Though after what I've just been reading about the Electrical Surge, I wouldn't mind betting that this took out the Fuse on the ABS.

If the ABS Fuse has Blown, then the Brakes would still work as normal except of course you wouldn't have ABS.

Which would mean that the ABS Light 'Stays ON'

So what 'May' be the best thing to do, is to Re-Check the ABS Fuse and then Re-bleed the Brakes, as it is now looking like your 'Electrical Spike' may have messed things up.

 

Simon,
Hearing more of the story I would definitely check the ABS fuse. On my 3.6 model it is in the fuse box above the passenger foot well. Regarding retention of error codes it may be that with no power to the ABS ECU the original error code may not be being cancelled out despite driving above 18 mph (or whatever the limit is). Let us know if fuse turns out ok and I will think again although away for 2 weeks from Monday.


Orangeblossom,
Thanks for the compliment but I am still very much finding my way with the ABS electrics but have certainly learned a lot in the last 12 months. I think there is far more skill required in taking valve blocks apart as you have done!


Cheers,
LeeP

 

Sorry I think I've confused people here with my last post...

The "surge" was while the car was still in it's garage over 18months ago. Everything in my first post was done in the last month.

I.e. I have checked the ABS fuse in the dash since the surge and its passing through the current. I have also changed the accumulator and bleed the low and high pressure pipes since the surge.

When I mentioned "but it could have easily also done for any inline fuses the ABS-ECU has between it and the ignition." I meant additional fuses that I'm not aware of, you know they some times pop them on the wire itself just before an important bit of hardware rather than in the fuse panel itself.

So the surge pretty much pre-dates this whole discussion, its defo a possible cause of damage to things I have not yet checked, but if I've mentioned checking them that is since the surge.

Once again sorry to muddy the water

 

Hi Simon

I'm now thinking 'Lee' is onto something.

Maybe you don't have a problem at all and everything is Ok, apart from the fact that the ABS light stays on.

Have you tried disconnecting the Battery, in order to clear the Fault Code and does the Brake Pedal feel 'Normal'

But having said that, I've just this minute thought of Something else!
There are a couple of Multipin Plugs, that Plug into the Valve Block/Actuator.

Where in the event those Plugs are loose or one of the Pins has got Corroded or Dirty, then the ABS Light will come on.

Which in that case indicates that the ABS isn't working, even though you may have 'Normal Braking'

So take a really good look at the Pins on those Plugs and Ditto with the Sockets they plug into.

You can get some Electrical Spray Stuff to help dissolve any Crud, so give them a really good clean.

This could very easily be the Cause of the Problem, so get a 'Mate' to watch the ABS light, while you 'Jiggle' the Plugs around in their Sockets.

Equally possible is a broken wire in one of those Plugs, where it connects to the Pin, it gets so hot in the Engine Room, that Wires can become very brittle and easily break, especially if they are pulled around, while you are trying to test them with a meter.

If all else fails console yourself with the fact today is Friday 13th!

I don't believe in any of that, except today I've decided not to go outside or leave the house.

 

I know nothing of this system, and proabably should "keep my mouth shut". However....


1. If the ABS is working correctly, a four wheel lock skid is impossible or close to it. ABS should release pressure just short of "lockup". Or that is my "understanding". My Jeep has ABS, but of a different genre...


2. The Jaguar ignition switches are far from robust. Many years of use and heavy key rings do them in. Strange things happen... Been there in my XJ wuzza 6. A good used switch fixed so many "oddiites".
It was so much "tighter" in operation. The old one was "loose".
I took it apart. Ugh, lots of contact wear and congealed goop.
Lost the "teeny" roller *****...


I hope this helps more than confuse.


Carl

 

PS!!!


Battery cable adrift!!!! Engine running. Oh, yeah, no dampener on the
alternator. Yup, lots of mischief...


Decades ago, I was driving in my IHD Scout II. A cable came adrift.
Engine continued to run. On alternator power !!! Luckily, I was blocks away from home. Made it. No signs of mischief. But, as a 79 model,
it's electrics were basic..... Great car, tough as nails. Lousy interior and tin!!!


Carl

 

Given we're talking other issues like the plug connectors in the engine bay are we saying the ABS-ECU isnt receiving power because of another problem and something else has cut power to it ? Is that something the system does ?

I was kinda of working with the fact the ABS-ECU isn't getting its main power as being the *problem* itself rather than a symptom of another problem. I was kinda hoping if i could restore power to the ECU the whole system may just come back. I was thinking maybe the ignition switch is somehow not transmitting power to the ABS-ECU when it's switch on, something like that.

I was reasoning it wouldn't matter what connectors "downstream" of the ABS-ECU are doing if the ECU isn't receiving any power to drive it anyway. Kinda like worrying about a keyboard not working, when the PC isnt switched on...

But from what you're saying you seem to be of the opinion that the problem is elsewhere and that's cutting the power to ECU or the ECU not getting power doesn't matter. Have I missed something ?

I might be approaching the whole thing from a too computer based angle, I do IT for a living and rarely get my "fingers dirty".

 

CadJag,

The ABS isnt working... that the problem, the system has detected some kind of problem and has switched off the ABS and has illuminated the warning light to tell me that.

The four wheel skid indicated the brakes themselves work - in terms of calipers biting discs. But the ABS isn't engaging. Sometimes when the ABS breaks at certain components it lurches to right or left. Also the ABS light could come on because the system has no brake pressure, that would make skidding the wheels impossible. So I was just using the skid to highlight that non-abs part of the breaking system seems to be okay, even if the ABS isnt happy.

I think my line "mechanically the brakes seem fine" is the cause of the confusion, I consider the ABS to be an "electrical system". So mechanically the brakes (master cylinder, calipers, pisitions, pads, discs) are working. It's the electrical side (wheel sensors, abs-ecu, valve block etc) that have a problem. Given the ABS system actually does a lot of physical work i guess your right its not a helpful delineation

 

One thing I've just thought of...

I'm using a Diagnostic.pdf i found on this site in another thread. I'm pretty sure i've established from the above issues that the usage of the pins on the ECU connector has changed over the years. It would stand to reason that if I have a diagnostic procedure from the wrong year then the guide will list the wrong pins.

I have an 89 XJR-S and the guide I am using is listing as being august 93. I wonder if my tests dont apply at all.

Really going to have to get my ROM cd working or just buy another

 

Hi Simon

From what I've just been reading, this isn't looking good!

If you can find a deserted road, Jab the Brakes Hard and Fast, as if you were going to do an Emergency Stop.

If the Car takes a Dive to the Right (or maybe to the left) this in itself could indicate that one of the 6 Valves in the Valve Block may have got a Blockage.

Which won't be apparent under Normal Progressive Braking.

This is something most often caused by installing New Callipers and Brake Pads, where someone has used a Lever (ie Screwdriver) to lever the Pistons Back to insert the New Brake Pads.

Without leaving the Bleed Nipples open.

In which case this can Force Brake Fluid, the wrong way up the System towards the ABS Actuator, which can cause the kind of damage, that you would not believe.

As it only take a tiny almost invisible (to the naked eye) piece of 'Crud' in the old Fluid to do this and in case you didn't realise there is almost certainly quite a bit of that, in the bottom of the Brake Reservoir.

Where even when it looks empty, isn't anywhere near to being as empty as you may think.

If this isn't caused by a Blocked Valve, then it could be a broken wire inside the Valve Block, which are actually 'Ribbon Connectors' that are so unbelievably Fragile, that you only have to look at them to break them.

Since you can't buy a New Valve Block, you would have to either rebuild it yourself or else get hold of one out of a Scrap Yard but in the event it comes to that, then get the whole thing complete, as if one of the Valves falls out, the weight of this is more than enough to break the Ribbon Wire.

So first try every single thing that you can possibly think of before you get into that.

With rebuilding the Valve Block, there is no guarantee of Success but having done a Few of these, depending on the Condition of the Valves inside, which could either be Clean or as Rusty as Hell, its always worth a try.

But as I have said, try everything else First, as rebuilding the Valve Block, is the Last Resort.

Come back if you need any help on that, in case push comes to shove.

 

Hi orange blossom

Apologie I must be explaining this exceptionally poorly.

I have already done the closed road test. She skids to a halt in a straight line.

I've also electrically tested the valve block and its returning the right signals

I've also audibly heard the valves each open and close properly with 12v applied

Further more from what I can tell my abs ecu isn't getting power so the valves won't be getting any signals to open or close anyway.

So I have non of the symptoms of a valve block issue. Even if I did my system isn't operational enough for me to experience the problem my abs is OFF.

So I'm really not understanding what has prompted you to think that could even be my issue.

Sorry if I'm being thick but I'm totally lost on your train of thought ?

 

Hi Simon

This is the bit that threw me into thinking that way, as I was wondering how you knew why it lurched to the Right or Left, if that had not happened.

Sorry if I misunderstood the way that you described it but when you finally get it fixed, please let me know how you did it.

The four wheel skid indicated the brakes themselves work - in terms of calipers biting discs. But the ABS isn't engaging. Sometimes when the ABS breaks at certain components it lurches to right or left. Also the ABS light could come on because the system has no brake pressure, that would make skidding the wheels impossible. So I was just using the skid to highlight that non-abs part of the breaking system seems to be okay, even if the ABS isnt happy.

 

Ah I was saying "I'm aware that it can be broken in that way, but mine isn't broken like that - as demonstrated by the striaght skid".

That was why I mentioned the skid in the first place, to show brakes are working and valves either aren't engaging at all or are working fine. I believe with my abs computer out of action my valves are just just sitting open allowing the pump to act as a boaster nothing more.