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Anti Lock ECU replacement

Posted: Fri Feb 15, 2019 1:36 pm
by MrScruffs
Hello Everyone,

I've been lurking on the board for a week or so, soaking up the expert advice and opinions of long-time XJ40 owners, and awaiting the sunshine to take some photos of my (new to me) 1989. Daimler 4.0 in lovely Dorchester Grey.

However, the photos will have to wait for the weekend when I tackle the ABS problem that is keeping it off the road. The Anti Lock dashboard light is permanently on from the first turn of the key. I picked it up last weekend as a running project with a recently expired MOT. Aside from the light being on she runs and drives great, with good general braking, no pulling in either direction, and a 'normal' feeling pedal.

Reading through the many topics here, and elsewhere, it would seem that the primary areas to investigate first are sensors, Anti Lock ECU, and an Over Voltage Relay? Although I think that my car as an October 1989 Daimler is actually a 90MY and has no Over Voltage relay? I certainly can't find one in the boot near the fuel filler!

My question is about the Anti Lock ECU. I decided that it was cheap enough to buy a known good replacement from the web during the week and fit it over the weekend before moving on to messier jobs. If I replace the ECU, should the light go out immediately or will I have to take her out for a spin to clear the warning?

Thanks in advance!

Re: Anti Lock ECU replacement

Posted: Fri Feb 15, 2019 1:57 pm
by katar83
My 94 ABS ECU was proper knackered, solder joints clearly cracked inside. I suspect earlier ECUs might have the same fault but resoldering it fixed is straight away. You will need to take the car for a drive to clear ABS codes.

Re: Anti Lock ECU replacement

Posted: Fri Feb 15, 2019 2:57 pm
by MrScruffs
Hi, thanks for the reply! Luckily I have a short private road right next to my house so I guess I'll be driving up and down that a bit to see if it works! :)

Re: Anti Lock ECU replacement

Posted: Fri Feb 15, 2019 11:06 pm
by naki_k
katar83 wrote:My 94 ABS ECU was proper knackered, solder joints clearly cracked inside. I suspect earlier ECUs might have the same fault but resoldering it fixed is straight away. You will need to take the car for a drive to clear ABS codes.


Agree yes. That’s certainly the first thing to try. Free fix, just your time.

Re: Anti Lock ECU replacement

Posted: Fri Feb 15, 2019 11:13 pm
by naki_k
The OV relay is for 3.6/2.9 models only.
Bit by bit they changed 90% of the parts on these cars between and early and late models.

Re: Anti Lock ECU replacement

Posted: Fri Feb 15, 2019 11:40 pm
by MrScruffs
naki_k wrote:The OV relay is for 3.6/2.9 models only.
Bit by bit they changed 90% of the parts on these cars between and early and late models.


Thank you for the clarification. I’m very slowly learning where she sits in the history of the model. There are lots of little jobs to do, but I believe that if I can get the abs issue sorted then I’ll be able to get an MOT and then spend a happy spring tinkering away...

...I suppose these are likely to be words that come back to bite me in 6 months!

Re: Anti Lock ECU replacement

Posted: Sat Feb 16, 2019 8:55 am
by MrScruffs
Well... it’s not the Anti Lock ECU... :(

Re: Anti Lock ECU replacement

Posted: Sat Feb 16, 2019 10:06 am
by katar83
Time to check each sensor now, have you got a multimeter and know how to use it? :ugeek:

Re: Anti Lock ECU replacement

Posted: Sat Feb 16, 2019 3:53 pm
by MrScruffs
I do not have a multimeter right now, but I did just do the blink test.

I got codes 21 & 32

21: defective valve/cable harness/power transistor in ECU.

Check indicated solenoid valve / terminals for short or interruptions

Indicated Solenoid: Main Valve

32: Sensor front right.

Re: Anti Lock ECU replacement

Posted: Sat Feb 16, 2019 7:36 pm
by naki_k
MrScruffs wrote:I do not have a multimeter right now,.


That’s your first issue to address then. That’s one of the most essential tools you will need to run and maintain a car like this.
You can get a basic unit for under £10.
I keep about 6 of these dotted around the place, so there’s always one to hand! They are that important!