I decided to start a new thread on this subject, even though it's related to the old Failsafe mode thread.

A few members have related that for the 1998 year model XK8 (and possibly others) the factory elected to install POMs rather than EPOMs in the ECM, which prevents reflashing of the ECM. Further, that as the car ages, the resistors fail causing all sorts of problems. So I decided to bite the bullet and purchase another ECM.

After an extensive web search, I decided to call an East coast Jag dealer that's been very helpful and reasonable in the past. They advised me that the ECM was not "plug and play" and that if the car wasn't hooked up to a dealer computer for reprograming the ECM to match the engine when it was installed - it would never run.

This is contrary to what another source advised me, that all they needed was the numbers off the ECM and they could supply me with a rebuilt ECM that would work.

Before I plunk down a sizeable chuck of my hard earned $$$, I'm hoping that some other members have been here before me and can advise me which is true. It's particularly problematci if it is necessary to hook the car to a dealer computer because there is no Jag dealer on this island. So I'd be faced with either shipping the car to the nearest dealer, or flying in a dealer tech and equipment. It's a toss up which would be less expensive and somewhat moot as either is well out of my budget at the moment.

Any advice is appreciated.

Thanks,
Oldfart

 

There is a part number for the ECM and then an extension (/xxx) that defines the programming of the vehicle. There is a TSB on compatibility of modules available above in the stickies. I would bet that a correctly matched part number and extension would plug N play.

I would also comment that after several years on this forum that there are very few real ECM failures even there has been lots of units replaced.

 

Agreed^^, not just for Jags but across the board. The only high incident failure rate I've personally seen was with mid-'80s mid-size GM cars (quad driver failure.) Some '80s Mitsubishi cars were also noted for a higher than normal rate. Altogether, for me, that means about 10 out of hundreds that I worked on. A couple EEC-III (Ford) boxes back in the '80s and one ancient Chrysler fuel injection box from the '70s. I've replaced a few SAAB boxes but they were either damaged or required because of lost keys.

 

Here is some reading for you

Certain VINs could not be 're-flashed' so read the TSB 303-S514am for the range of cars/VINs.

The throttles are an example of the NON-flash ECMs.

bob gauff

 

Thanks for that info. What you're saying is pretty much what one source told me. First, I'm going to change the Transmission Rotary/Neutral Safety switch (ordered it yesterday) and see if that exorcizes the demon. At the same time it's in the shop for that, I'll have them remove and open the ECM for a visual inspection. A prior thread advised that it's pretty easy to spot failed components. If it looks good then maybe the rotary switch is the cure.

Thanks for the help guys.
Oldfart

 

The Tech Bulletin on Control Module compatibility is very useful and many thanks. Now I know where to find the VCATS number for my ECM and can both verify whether the original is still in the car, and place an order for a new one (if needed) that will be a correct match.

Never would have thought to look on the floor of the spare tire well for this info that's for sure.

Thanks again for the help.
Oldfart