Hi, I'm new here I've joined to see if anyone can answer this question. My engine ECU no. Is 4R83-10K975-BA what do the last 2 letters signify? I've looked for a replacement on ebay etc and there are several with different letters at the end instead of BA like mine. ie AA, AF, BH .... any help would be much appreciated! TIA 

I'm not sure on Jaguar ECUs but i know Rover 800 ECUs the last two digits denoted a build code/date so arguably could be interchanged (subject to reprogramming for the immobiliser etc) and on Fords, it was the "Finis Code", almost the same thing i believe.

Hopefully someone will be along soon with more in-depth knowledge of the Jaguar numbering system.

Thanks for taking the time to reply 😊 according to a jag dismantlers on Ebay the number has to exactly match, so I've now located and ordered one that does! 😎

Excellent news - i wasn't sure on the matching numbers bit, on some Rover 800s they absolutely have to match, others can be "near enough" and as i pointed out, i'm not sure on Jag ECUs at the moment.

Hopefully your new ECU will get you up and running again! 😉 😄

7 minutes ago, LairdScooby said:

Excellent news - i wasn't sure on the matching numbers bit, on some Rover 800s they absolutely have to match, others can be "near enough" and as i pointed out, i'm not sure on Jag ECUs at the moment.

Hopefully your new ECU will get you up and running again! 😉 😄

I hope so too. It's an intermittent fault dash lights up light Blackpool illuminations, revs go to around 2500rpm. The only solution is to turn off, remove key and wait 20-30secs, until all lights go out then restart the engine. My local indy garage said it showed as a tps fault which they replaced, but then it still happened occasionally, then they thought it was a break in the wiring (5v reference supply) which they bypassed, said its had a few test drives now, no problem, the next day after I collected it, it happened again! 🙄 now they're saying it can only be the engine ECU around £1400 new 😳😳 they were waiting on getting one from the local Jag breakers, but I managed to get one on Ebay for £150 (was £199, or best offer) along with 11 other items included :-  dash, ignition, keys, door lock, boot lock, other electronic modules (BSM's ??) Etc a good deal, especially as a breakers in Liverpool wanted £240 Just for the ECU 🤔 now it's booked in again 4th July. Another strange thing is if I apply the handbrake at traffic lights, junctions etc when stationary, it seems to trigger the 'fault' as I've not done this since, except when parking it hasn't occurred again so far (touch wood). I did pass on this info, but was told there's no connection between the h/brake module and the tps, but as I pointed out, when the h/brake is on and you press the throttle pedal it disengages the brake, so there is some sort of connection? We shall see after the ECU is changed. I will update this post when there is more to report 😎

You may well find you need most of what's there, if the ECU is coded to the key you can hide the key behind the steering column cowl and it should bypass the immobiliser for you.

Yours is a later one with electronic parking brake then? There must be some connection from that to the ECU so it releases when you apply throttle (i'm guessing it's auto?) so that you can drive off.

I hope the garages diagnostic process is correct, at least you'll have a spare set of ECUs/modules etc if not.