richardpope50

I have a problem with my ABS ECU module that appears to report a self-test problem but I cannot find out what it is. Can anyone help?

I have performed all the checks given by ‘jon@work’ in this old thread

https://passionford.com/forum/techni...wd-cossie.html

and it all checks out so I am puzzled.

Ignition key to ‘accessory’ and the pump activates and stops when pressure reached.
Ignition key to ‘ignition on’ and the amber warning lights correctly come on but do not goo out. Up to a couple of weeks ago they did and all has been fine for years.

The self-test would appear to check

1. The low fluid level and pump accumulator pressure circuit that says the pressure is up (and it would appear to be so as brakes work normally
2. The ohms across the valve block and this is within spe,
3. The ohms for each of the four wheel ABS sensors and all are within spec.

What else does the self-test check?

I have also checked the ABS (green) relay 3 via a jumper and this is OK too. It thus seems that the ECU module is not passing the self-test and thus not triggering relay 3.

FYI. The Sierra diagnostic socket does not report ECU module error codes as there are no connections to the ECU from it. I have checked all diagnostic socket pins and they all check out too. For completeness, I borrowed a Crypton diagnostic kit from a friendly garage and this showed no error codes but given the above, that’s not surprising.

Yes, it could be the ECU module itself but they are supposed to be very reliable (but perhaps not 100%).

Any help really appreciated

dojj

iTrader: (3)

I had a dodgy wheel bearing which goosed the sensor
But nothing showed up until I needed to brake and nothing happened
It's normally a sensor or the relay
That's are easy to swap
If all else fails unplug the ECU for a couple of minutes and see if anything changes

richardpope50

Thanks Dojj but all sensors test out with correct resistance and this happens without the car moving. Removing ECU does not make any difference either. It cannot be wheel bearings nor the ABS rings either.

dojj

iTrader: (3)

have you tried the pressure switch?
from memory it's the green one with 5 wires coming out of it
the only issue is that if you undo it the dissimilar metals tend to strip the threads

4x4kiwi

Was going to put up a pdf for the '87 ABS system test manual in case it was of some use but I don't know how to attach a file. Anyone know how to do it. David

dojj

iTrader: (3)

Will the picture attachment thing work?

richardpope50

Thanks You have PM.

richardpope50

Wel, there has actually been a saga. I posted a few weeks ago about binding brakes and in trying to solve that issue suddenly the ABS ECU self-check lights stayed on. I'm not sure if I have cured that issue yet but my have.

Basically I changed the main actuator (master) unit and that did not cure the binding but led me to think the pump unit was faulty as there appeared to bee too much pressure in the system. (Binding was temporarily solved but I had a (very small) leak between pump and main unit. When done up the problem returned.)

I changed the whole pump unit but could not bleed it. Took off 'new' pump and decided to change pressure switch. But I found the threads crossed so could only replace my original pump. As that had apparently not worked I used a spare pressure switch I had (off an XR4x4, actually - red one). Changing one item at a time to see what failed / worked.

I think it was then that the self-check failed. I then changed back to my original green pressure switch and I still have the self-test problem. That's where I am today.

Whilst it is totally a Sierra ABS system, it is actually in this ...


FYI: 5.0l TVR Griffiths V8 (originally Rover V8)

martysmartie

iTrader: (1)

I think the switch is fine...

If this were a problem, you would have the fluid/parking brake brake light on, the light you have is purely for the ABS, with the sensors being the most common cause.

Have you checked them at the ECU itself?

Martin

richardpope50

Thanks.

1. Agree except fluid light is the amber one as it is in series with the pressure switch, and the red handbrake light is controlled by ECU and has never come on.
2. Yes. Three at about 1060 ohms and one at 1200 so changed that to one at 1100 ohms and still amber lights on.

Aa I say, all tests in the jon@work posts check out 100%

Interesting point, it has always taken 60 seconds to pump accumulator from cold. However after changing for first red switch and then going back to the one I had been using it now takes about 20 - 30 seconds to pump up. The only other thing I did was to take off and put back the accumulator sphere. Probably nothing but curious never the less.

Still absolutely puzzled.

Turbosystems

iTrader: (5)

The red hand brake warning light is the low pressure warning light and low fluid warning.
The amber light indicates an abs error and can come on independently and when the red warning light has been activated.
If the fluid level is low or the cap is faulty this will activate an abs warning and illuminate the amber light too. To test the cap you simply need to bridge out the 2 pin plug

4x4kiwi

Have sent you an Email which hopefully has an attachment that you can access. File was too large to attach in the normal way.
Also not sure how useful it will be as I think it uses a Ford breakout box to do the measurements but I believe in conjunction with a circuit diagram it can be used.
In the past I had a problem with the ABS light coming on - but I believe from memory it was only after starting moving. The resistance between the two wires of the sensor read O.K. as yours do but the earth shield is not at earth potential and was shorting to earth through a chaffed outer insulator. At the ABS module connector check the resistance between the earth shield side of the cable and actual vehicle earth and see if one reads different to the other 3. Just a thought.
David

4x4kiwi

Just noticed Richard if you do get the file that it is all backwards i.e last page first. I will try to fix it up when I am back at work and re send. David

4x4kiwi

Resent in corrected order and split in half to allow attaching normally.
David

richardpope50

Thanks for a copy of the manual and it does appear you need a breakout box as they do not give conversion between breakout box pins and ECU plug pins.

My ABS warning lights will not go out after self-check. This is when car is at rest with ignition on and engine not actually running - having the engine running makes no difference as it is all electrical.

I'll check the earth shield and actual vehicle earth but all my problems with this ABS warning light staying on have been with car on the blocks and whilst I was changing the pump unit.

richardpope50

Whilst some manuals say this, actually the circuit between ECU pins 9 and 10 makes a circuit to the low level fluid switch and then the pressure switch and back to pin 10 all in series. Thus it would appear the the ECU can only check these two are OK together and cannot differentiate between the two. I have never seen the red handbrake light come on (apart from handbrake being on).

My fluid level is at max anyway.

As I say elsewhere, this ABS warning light problem only started a couple of weeks ago after changing (and fiddling with, I suppose) the pump unit.

4x4kiwi

I had a quick look through and the checks from page 75 to the end definitely tie up to the normal ABS Module pins according to the cct diagram. Unfortunately these are mostly the same checks that Jon @ work has already listed. I am assuming you do have a diagram of the system. I have not traced through the cct to see what the effect of a shorted or open diode would be but I do see there are a few diodes in the system, including one in the warning indicator circuit. Have found in the past you can sometimes use these system test manuals to work out what part of the system they are checking with the breakout box and finding that item on the circuit diagram and finding which pins on the module to check on. Cheers David

richardpope50

Thanks David. Yes, I have several versions of circuit diagrams.

Yes, I checked one diode (as per jon@work) but will try the others too.

Thanks for suggestion, yes, I work through the tests and see if they are the same ECU pins.

I'm beginning to think that the ECU module may be faulty and will get a replacement anyway. Whilst I have a 4x4 ECU, it is marked 4x4 only and the compatibility roll pins either side are different to my 2wd version, I don;t think it is worth trying to use it even though it will probably tell me if the self-test is blown.

(Shame you are not just down the road from me!)

Richard.

4x4kiwi

Yes a bit too far away - 11,617 miles actually. Mine is also a 4x4 anyway.
Another thread here that jon@work also details the tests which I assume are the same as in the other thread although written differently. Interestingly the problem was the light never going off but turned out to be a sensor. I was under the impression a faulty sensor would only bring the light on once moving.

https://passionford.com/forum/ford-s...ossie-abs.html
David

richardpope50

Thanks David, for link to post. Appears the same set of tests but will go through them in any case.

My amber warning light problem has only happened whilst the car has been on axle stands. When I got the car off blocks for the summer, all worked except for binding rear brakes. It has basically been on axle stands since April trying to sort that out with a few very short test trips. The amber lights never came on except a few weeks ago when suddenly they did not go out after one of the times changing the pump unit (and still on the stands). Apart from about a mile or two's test trip when they did not go out either, this all happens when on stands and ignition is turned on.

All my wheel sensors check out with 1060ish ohms. One was 1200 but I have temporarily swapped it for one of 1100 ohms in case that caused it. Made no difference.

I think the self-check checks the sensor ohms and when on the road, ECU is always checking for the voltage being the suggested AC voltage check / test. Since my problem is at self-check time, I cannot see sensors being the fault. Yes, for others it usually is the problem.

Having bought an ECU so I'm changing that next apart from going through all those tests again.

Richard.

2Litre

Evening Richardpope50 - I know this thread is a couple of years old but I have exactly the same self test/ non energising green abs relay as you had. I to did all pin out test which all proved to be in order.
My question to you is did the replacement ECU solve your problems?


Thanks in advance.

Tim.

richardpope50

Hi Tim, I'm afraid that the answer is no! First point is that I actualy installed the Sierra ABS system on my Dax Rush (se7en) kit car. For the first three years everything was great. Then the brakes started to bind and basically locked on. This was random but when they did, I had to wait half an hour for them to unbind then all was OK again. This plagued me for over two years. I changed just about every ABS component I clould including ECU, actuator, and pump. In the middle of the two years and whilst I had just chenged the pump the ABS (yellow) lights stayed on and would not goo out. Up to then it always did. No idea why. I even changed the pump back again but still I had the light fault. Everything I did did not cure the binding brakes nor the ABS lights. In the end just this last March I had no choice but to remove the whole ABS system and put the car to 'normal' brakes although I did add a dual circuit servo. I am pleased with the result although I do not have ABS, obviously. I assume you cannot really do that.

Really sorry I could not help you. By the way, I even tried a Ford diagnostic computer but they do not work on all versions. It seem only Cossie and Transits! Looking at the diagnostic socket wiring diagram it makes no sense as it does not even have a wire to the ECU. If it had, it would allow you to clear the fault as well as probably identifying it.

Hope yours sorts itself out. I have an awful lot of ABS test information I could e-mail you if you want. PM me.

Richard.

2Litre

Thanks very much Richard for getting back so fast! I would really appreciate any info on system, E- mail as follows - timbliss03@gmail.com
Do you still have any of the ABS parts you removed?


Once again thanks very much for getting in contact.

Best.

Tim.

Adam-M

Do you know if it was binding the front or the rear brakes?

Gavin E-Cos

My understanding of this system is that the fault codes must be read first, then the car driven above 25mph and if No more faults are detected then it should clear and reset. I'm trying to find out how to read the codes?