Finding the correct ECM?

(Mr. Phelps) #1

Hello, My mechanic had a heart attack this year which stopped all work on my 1995/6 XJ6. We have tracked my problem (no idle control) to the ECM that was replaced by others. result is I do not have the factory ECM ID to enable me to order a replacement from some of the many sources I see online. How does one find the correct ECM without the old one in hand? I know the replacement is incorrect as it has the wrong outer shell for mounting, Im reluctant to try to have it repaired if its the wrong unit inside as well. there is no signal going to the throttle control, checked with NOID light today. everything else on the car works perfect, a one owner car until myself and well cared for till the ECM was replaced.
TIA,Steven Phelps
Vero beach Fl.


(motorcarman) #2

Just get a used part from a salvage vehicle that is the SAME as yours.
The list of PROMS is in the Recall T493/R493 if the procedure was carried out during the campaign you should see the part numbers on the case and PROMS

I’m pretty sure almost all the ECMs are the same, it is just the PROMS that are different for models and years.

Here is a copy of the Recall we did in the late 1990s/2000s

05-1-26am5 1995 MYRecall R493.pdf (256.2 KB)



2005 XJ8 but ECU has mismatched VIN
(Mr. Phelps) #3

thank you, sounds like you know what yore talking about! I cant get one the “same” because it’s the wrong one. the mounting tabs are wrong for my chassis. who knows what it came out of! but its quite similar and I think I can identify a correct case if I see one. there’s a couple on e bay now. one warrantied.
sorry all, i thought these were private messages as they came into my mailbox , confused here as usual
Steven Phelps


(Mr. Phelps) #4

I found a warranted unit for a 1996. my car is titled 1996 but manufactured in late 95, common for models to be made the year before. do you think id be alright with a 96? as you said it looks the same. I’ve discovered the difference in the case on the one on the car is due to the rebuilder installing the back cover upside down. that placed a mounting tab where it should not have been. the installer cobbled up the install because of that error. worst part of that and probably why it didn’t work was that the chassis ground which was supposed to be behind the ECM case mounting bolt was not installed. they put the ground wire on the case with a small screw accomplishing nothing especially if you consider the case was poorly mounted with only the rear mounting bolt and that not very tight. intermittent ground at best worse than none at all IMHO.

sorry to ask so many questions , your original instructions quite clear.



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(motorcarman) #5

The bad thing about not being intimately familiar with something is that if someone previous assembles something incorrectly, you just put it back together the same ‘incorrect’ way.

I have done things like that in the past. When you finally find a diagram or another part in original condition, it all becomes clear that somebody before you ‘screwed-up’.

good luck.



(Mr. Phelps) #6

opening up the old ECM case i found several circuits shorted out on the board. moisture when the rebuilder had it apart (same guy that put the case on upside down) ? Im going to check circuits see which pins those connect to. Have to get a special security torx bit to separate the boards. its on the red plug is all i know for sure now. replacement arrives next week, plenty of time to study some more :slight_smile:


(Mr. Phelps) #7

I should report that i followed advise given here, purchased a used ECM from a wreck and another to have as a back up that was also salvaged but guaranteed. Installing the one from the wreck I am now driving the car. I posted some information on “ECM missing parts” about these ECMs but its hard to follow unless you’ve see one in hand. I think those parts are very important.
Thanks to all who helped me get my car on the road!

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