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[Andy H]

I still think you have the common fault where the aluminium wires break inside the ECU. I know you have tried another ECU that was working in a previous car but you didn't get that one on Tech II to see if it was showing the same fault as the ECU that is in the car now.

I worry that you have made unnecessary work for yourself by attacking the front wheel sensor.

I would still recommend getting your original ECU fixed by BBA reman.

For the best price on a genuine front wheel sensor I would contact andyc.

[terry paget]

Thanks Andy H. You could be right of course, though it seems unlikely that  a spare ECU of good history should demonstrate a similar fault. I suppose I could swop ECUs between cars, but my only other 2 litre manual R706FHD is the spare car I gave to son Jonny while I prepare his for MOT. He lives 20 miles away. I forget how much ECUtesting charges for a 'test and find no fault' service. I suspect it was £100, same as for a repair.

I still have on the bench the ECU that I exchanged before. If I swopped that with the ECU in R706FHD that would settle it.

[terry paget]

Have just fitted a used front hub with ABS sensor. ABS light stays on, after 2 mile test drive. Is it ECU after all? Could it be nothing else?

Is there any point in putting back the other ECU?

 

[Kevin Wood]

It needs proper diagnosis, IMHO. Could be ECU, wiring in vehicle or sensor.

Replacing the ECU with one from a scrap car isn't conclusive, IMHO. They all fail at around this age. Plenty of cars probably get scrapped at this point because they go to a main dealer and get a four figure quote to replace it with new. The chances of a second hand ECU also being faulty are not minimal, IMHO.

[terry paget]

Thanks Kevin. I agree it needs competent diagnosis. I simply cannot think how to get one. I agree the fault must lie in the ECU, a sensor, or the vehicle wiring. The ECU I substituted was not bought from a scrap yard, I removed it myself from a car I scrapped last June after a failed water pump wrecked the engine; the ABS was working perfectly then so I assumed the ECU was OK.

I recall you suggested I should take the Tech2 man for a drive and let him compare sensor inputs. I doubt he would do that. I could put back the substitute ECU, then go back to him with different ECU and right front sensor and get a new Tech2 readout. Would that help?

[Kevin Wood]

I think I would check that the resistance of the sensor can be seen between the ECU pins where it connects first. That way you can be confident that the wiring to the ECU is OK.

But.. when it comes to diagnosing further with the Tech 2, you only have to go round the block checking each wheel sensor input. In a straight line, they should all read the same speed.

The classic ECU failure results in a failure to even connect to the ECU for diagnosis, so it looks hopeful in that respect.

[05omegav6]

Silly question, but are both front tyres the same size

[terry paget]

Hi ex taxi al. Sensible question, but, sadly, all tyres are 205/65 R!5s. Worth checking.

[terry paget]

Hi Kevin, thank you for your thoughts. I did check pins 4 & 5 at ECU connector, as advised, and these indeed did show 700 ohms, and when I unplugged front right sensor to loom connector they went to open circuit. The Tech2 had said it could not see front right sensor. I saw no reason to doubt the other sensors were connected OK.

I cannot imagine why the wheel sensors should record different speeds if they are working at all. The tyres are an assortment, all nominally 205 65R15. I have run on assorted tyres for years in all my cars, including mixing sizes on occasions, without ever upsetting the ABS systems.

As suggested before, I wonder if it is worth while swopping the ECU again (the one now in the car is the original one) and asking the Tech2 what it sees then, with a different front right sensor and a different ECU, and having established connection between front right sensor and the connector socket, and having different aluminium wires from ECU connector plug to PCB.

[sassanach]

well either my multimeter is duff or 700 ohms is 800 ohms short off where they should be,the two i have here both read 1500 ohms and i know there okay.incidentally its no use sending pm's if you do read the replys or answer your phone!!

[terry paget]

Hi Sassanach, thanks for you reply. Apologies for not collecting my message, I am new to the intricacies of the OOF, but am learning. Funny no-one answered the phone. Thanks for the message.

I am not sure of the actual value of the resistance of my sensors, they fall between ranges. Main point is they are all about the same, so it's a mystery that the Tech2 could not see the front right sensor, because it was the same resistance as the other three sensors, and it was connected through to the ECU socket. Where I go from here I do not know. Sleep on it perhaps.