Hi, I'm thinking of buying a spare used ECU for my 2005 XJR. I was looking at the ECU serial number and comparing it with some that are available on sale on e-bay and I'm wondering, how does one know exactly which replacement ECU is suitable. I've attached pictures of three ECU's, all of them for the XJR and their ECU numbers are almost the same, except for the last two letters. Are these last two letters important or are they just batch numbers? Does the ECU number have to fully identical? I can't tell from the parts list as the list has SAJAC numbers, which don't seem to be reflected in the pictures of ECU on sale. Can anyone shed some light on the numbering system of ECU's for compatibility purposes? Thanks

 

You know none are just plug n play, but will need suitable reprogramming (with care, IDS/SDD, hefty power supply, etc)?

 

Thanks for your comments. The standard IDS can do the reprogramming right? Does it matter then which basic ECU I use? Apart from the gadgets like the hifi system, do you know what engine and transmission items needs to be configured? Are the basic maps stored in the IDS system?

 

Why are you wanting to start down this painful path which risks leaving your car bricked?

You can do a lot of reading on IDS... but why bother...

 

Fully agree with JagV8 - why are you looking to source a "spare" ECU? They are usually robust and only fail with user intervention with sub par dealer level equipment/experience.

 

Hahahahaha.... maybe I'm just overly cautious about having backups for electronics, especially when it's such an important item....... I have three back up ECU's, all identical, for my 1992 Mitsubishi GTO..... It also helps in trouble shooting....

 

Things were much much simpler back then.

 

klfong here are a couple of links to ECU/ECM replacement threads that might be of some help or at least offer a hint or two. In the past I have replaced modules (NOT ECU's) and I have stuck to the belief that an EXACT match is the safest way to go. The numbering system, including the last two letters is there for a purpose. It's very likely that those last two tell us that they particular module has different native programing to either do something different or to mesh with other existing hardware due to different options, different laws in different countries, or some other obscure nonsense. This would be especially true for ECU/ECM's I suspect. In the U.S for example the 4.2 non-SC cars are limited to 121 mph while the SC's cars are 150+ mph.

https://www.jaguarforums.com/forum/x...cu-pcm-185369/

https://www.jaguarforums.com/forum/x...cement-225633/

 

Thanks for your links. Sounds scary though. All the more reason to have a backup unit done, ready and waiting, while there is no problem with the original unit as I certainly don't want the car to be immobilised just because of an ECU problem. Hence the aim of trying to find a suitable one to be the back up. From the additional e-bay pictures that I put up to compare with my original, all the ECU's are for the supercharged car, but which is the actual part number? Is it the MB07970-XXXX number or is it the 2W93-10K975-XXnumber? Does anyone know?

 

Expect to need IDS/SDD and that connecting a different PCM will put the car into anti-theft.

 

Thanks. Fortunately I do have a set of the IDS/SDD done by CAMBO, which has been very useful.

 

"If it ain't broke, don't 'fix' it."

 

Hahahaha... thanks... I believe in having back ups where possible, but the general feedback seems to be not to...........

 

As an idea it's great, and if you're happy to risk immobilising the car so you need a Jag tech to fix it, have fun...