I repaied a dead vehicle ECU once by simply re-soldering the joints inside. The power drive to the fuel injectors went through soldered joints & sure enough, they had fractured. A quick repair with the soldering iron & everything worked fine again.

So why do they fail like this?

Well, for reasons of vehicle production speed, the joints are made using a flow technique so that mass-production can be carried out in a speedy fashion. The joints formed are electrically alright but mechanically weak, as there is not much solder on the joints.

After several years of mechanical vibration in the car, the joints weaken & fracture, causing intermittent & then permanent electrical faults.

The repair is often simple-as in the above cases. By re-soldering all the suspect joints properly by hand using a more substantial amount of solder, the joints are then strengthened mechanically.

This is particularly important on PCB's where the joints carry high currents-such as in ABS control modules & the output stages of ECU's which drive the ignition coils & fuel injectors. Very often, complete & very expensive electronic modules are replaced when the actual internal fault is very simple & cheap to fix.

Solder joints are one example-the other examples are the power transistors in the ECU output stages which drive the external high current devices like fuel injectors etc. The output transistors are really very cheap to buy & replace-the hardest part is finding the fault if you don't have the circuit diagram.

But as a general observation, re-flowing the bigger solder joints inside electronic modules often cures the fault, particularly when actual connectors are soldered to the PCB. These are often under high stress when plugs are shoved into PCB-mounted sockets, as the mechanical force can weaken & fracture the shallow solder joints.

So if your electronic module doesn't work-open it up & closely examine the solder joints for circular hairline fractures on the bigger joints. Then just re-flow the joint with more solder to make the joints mehanically much stronger.

It's a lot cheaper than a new electronic module

 

Many thanks for this post. I just finished resoldering the ABS module on my 1999 XJ8. I was able to saw off a portion of the lid on the unit to gain access to the joints. This meant I didnt have to remove the module. Soldering the joints was a little bit tricky but using a small mirror and a steady hand, I successfully managed to get to them. Job took about an hour total. I glued and sealed the portion of lid I had cut open with clear silicone.

 

I've just 'done' mine today. Bought the car on Wednesday and it had 2 ABS modules as the previous owner had slaved one in electrically in order to pass an MOT test. A bit dodgy, me thinks!
Anyway, I took the ECU off of the unit which was electrically connected, because when I plugged the harness into the one which was plumbed in, I got further errors including "Incorrect Part Fitted".
Before swapping it to the plumbed valve body, I dismantled the ECU (which involved some brave use of an old chisel and a small hammer). It would appear that the two halves of the case are sealed with a rubber grommet and this, over the years, effectively bonds the two halves together.
A quick visual inspection confirmed that the usual 2 pump power pins had fractured, so a quick session with the soldering iron fixed them. Then I resealed the box using high temperature silicon goop.
I then managed to swap out the ECU from the plumbed in unit with this renovated ECU without unplumbing anything. After moving all the nearest harness and relay gumf out of the way, undoing the three mounts bolts on the assembly and also removing the clips from the pipe run along the longitudinal, you can just about bend the pipes enough to gain access to the star-head bolts and then remove the ECU.
Anyway, with the 'new' one back in - I also got the same errors up on the dash on the first ignition cycle, which was slightly disheartening, but I cleared all the codes, did a couple of ignition cycles and it all seemed to have cleared.
So then I took it for a spin, found a gravelly farm track and put my foot down. Ta-da! No wheelspin, and then a full ABS stop from 50!! Well pleased.
The ECU I've taken out, I think has further issues as it is reporting itself as the wrong part and also doesn't seem to be transmitting the fluid level to the dash. I'll keep it as a spare for now.

In summary, don't be scared of the ABS module - if you can solder then it's an easy repair and could save you a lot of beer tokens to do it yourself.

 

Hi all, does traction control failure and/or ABS failure cause restricted performance ?

 

Did not cause restricted performance in the case of my UK spec Daimler Super V8. However, I had only brief occasional losses of connectivity to the ABS pump motor (the solders issue). Perhaps the restricted performance will come in if there is a permanent loss of this connectivity (or some other permanent fault). Or, perhaps, the restricted performance activation depends on which country the car spec is for.