Hello, I'm still having a problem with P0300 multiple cylinder misfire on my 96 XJS convertible. Misfire started after mechanic said it was my ECU module. He purchased a used one from the wrecking yard and replaced my original one. I changed the ECU unit back and found that the one he had replaced my original one with was out of a 95 XJ-6 sedan. I'm getting conflicting information. Some folks are telling me that they are essentially the same yet the numbers are not and the re-manufacturing companies are also telling me that they are not the same. So, are these two ECU modules essentially the same but with different part numbers?

 

Here is some info for you to read. I doubt the PROMS are still available but you might find a unit that has been updated and has the modification label.

bob gauff

 

Thanks Bob, I check with the dealer and they looked up my VIN no. and found that my car had been updated. I replaced the used XJ6 ECU with my original and guess what, the problems I had been having are cleared up. My ECU module is fine and the car no longer misfires nor does it give me any OBD codes. I copied the Jag Bulletins you sent me. Great information!
Jorge