Are the ECUs between an XJ6, and XJR6 and the various regions all the same except for their ROMs?

I'm looking for and having a tough time finding a replacement ECU for my XJR6 to do some testing, and wondered if perhaps I could just use an XJ6 ECU and swap over my ROMs?

When I had the EGR recall done a few years ago, they updated the ECU by installing a new set of ROM chips. So that makes me wonder if perhaps the base ECU is the same for NA XJ6 and SC XJR6 cars and the only difference is in the ROM set.

I know for example this is true of early to mid 90s GM 3800 equipped cars. I changed out the ECU on my Buick Riviera twice with ECUs from other GM cars, and just needed to move over the ROMs.
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Hello XJREngineer

Maybe post numbers, photos, etc from the module (& its chips) in the hope another owner will share.

The engine ECU hardware is common across all 6 cylinder X300s. These is a service bulletin on how to change EPROM.

Al Roethlisberger
If you email me directly, I'll send you the service bulletin on how to change the EPROMs.

Thanks Andy, I'll drop you a note. That is EXTREMELY good and helpful news... and what I suspected.

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Al ,

In your quest in writing the book on Jaguar AJ16 Engine Control and Practices you are in the final chapter in bringing it all together .

A note on your throttle down stalling is the ECU orientation or setting to your TPS value at idle closed stop position . You mentioned in previous post you may have changed the TPS and it's new reading in it's physical mounting position may be different then the original . This could cause a mismatch causing the ECU to underfuel the engine in this idle region . The manual specifies that it's reading should be 0.60 + or - 0.02 volts on the Green / Yellow wire . You can test this with the engine not running but key on . Move the throttle and you will see it climb towards the ECU reference voltage of 5.0 volts on this sensor . While you are there verify that you have a smooth change in value as you slowly move the throttle and what you don't want to see is a bip or spike on the meter value . Mine was at 0.63 and had to drill larger the mounting holes to be able to twist and put it on exactly 0.60 volts . Regardless of where yours is at at this point or the previous point is irrelevant . It is the matching of the sensor's reading at the time the ECU was oriented to match the previous sensor reading at closed position .

You can see if it is underfueling with your devise by looking at the STFT and seeing if it goes below 0.0 % . It will fluctuate a bit as the ECU can only adjust in data value increments based on the limited number of maps or data arrays it can store . You don't want a pattern of below 0.0 %

Without doing the orientation and the cost and equipment involved you can twist the TPS and retighten the mounting bolts on a trial and error basis as you test drive it and noting your results . Your original closed stop position may have been 0.58 or 0.62 , you never know .

This notion would invalidate the swapping of a different ECU's as a plug and play as you would not know where it's orientation is at to match a 0.58 or 0.62 sensor reading of the donor car .

There is probably a better way to explain this and I could be wrong . Contributors welcome .

Notice that this does not include the O2 sensor / ECU orientation that I don't have a clue about .

Thanks, but I did not replace or remove/loosen the TPS at any time since I've owned the car.

I do plan to get a TPS and O2 orientation performed if I can get the car running reliably though. I may replace all the O2 sensors at some point just because, and it will make sense to get the orientations performed then.

I attached some data logging to my main thread, so one can see the STFT and TPS% there.

I picked up a 1996 and 1997 XJ6 ECU from a wrecking yard today. So I'll take a look at moving the EEPROMs over to do some testing.

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It may according to theory be possible to replace one sensor at a time with X number of miles and cycles in between the next sensor change and might get around a O2 sensor orientation . This instead of all 4 at once requiring ( ? ) a orientation .

One of my downstream sensors wiring was damaged with wiring broken and sticking out of the insulation as the PO din't keep it from twisting during removal and installation as well as smashed sensor cans from channel lock plyers and both bosses cross threaded and galled . Lady P was a toss in on someone's truck deal in her past ownership ..

The most important thing in EPROM swapping is your fingers or tools static electricity . There should be a sticker on the ECU if the EGR is remapped with the upgraded EPROMs

Andy is this true of all the LNA1410xx/xxx and LNB1410xx/xxx seried ECUs from 1995 to 1997 that the engine ECU hardware is common/identical, and the only difference is the EPROM?

I have an ECU from a 1996 XJ6 dated 09/11/95 which is an LNA1410VE/102

I also have an ECU from a 1997 XJ6 dated 12/08/96 which is an LNB1410AC/101

I just want to double check that the LNA isn't an issue so I don't mess up my XJR6 EPROMs or any other electronics in the car.

I dropped you a direct email and PM here for the EPROM replacement instructions.

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TSB T493 / R493

http://www.jagrepair.com/images/TSB/...all%20T493.pdf

I believe I have a non-recalled ECU in my possession. It was in pretty rough shape. I have never tried plugging it in, but it does not have any of the familiar recall stickers I have always seen in the past.

Are eprom chips still somehow available?

The 2 ST Microelectronics brand EPROMs are available on Ebay about $ 4 dollars each and a EPROM connecting dock station for around $ 50 including cables and software as well . Copy and paste the data maps .

https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=microelec tronics+eproms&_sacat=33543

https://www.ebay.com/itm/NEWEST-PCB6...pe!64155!US!-1

In my opinion they widened the opening schedule of the EGR for more un oxygenated gas to flow back through to meet EPA emissions targets on a round trip all ranges basis . But this as the valve is open reduces the effective displacement of the engine cylinders sacrificing the total power available . In the VVT setup you have better exhaust gas clearance and retain the effective displacement at high RPMs .

The EGR replacement is for maybe more in service reliability or matching of the ECU commands .

Mine was never modified and I'm not in a hurry to do so . Buuuuuuuuut in the future looking to increase to EGR valve port size and scheduling step feature of the opening to bring in fresh oxygenated air above X RPM ( blanking the exhaust manifold ) so the TB does not restrict the air amount into the intake manifold . This would require tweaking and biasing the ECU maps as it schedules open without noticeable engine stumble and mixture leaning to stay under a sustainable EGT for the valve part numbers . Don't know if this has been done before or if feasible .

A guy's gotta tinker .

EGR is not used at wide open throttle, so does not affect performance under these conditions.

You'd need to contact your dealer to see if the VIN for the car has had the recall performed. I'm not sure you can get the EPROMs by themselves, but I think you'd have to ask a dealer.

I had the R493 recall done on my 1997 XJR6 about 3 years ago, and at that time the EPROMs and replacement throttle spring were still available. For my car the recall included a new EGR valve as well.

See: https://www.jaguarforums.com/forum/x...recall-126057/

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My VIN has had the recall performed, its a spare ECU that I have acquired over the years that has not....

I didn't think not having the recall performed would hurt it's value as a backup/spare.

Thanks.

I'm assuming that since I think it was you mentioning the valve is closed at idle you can remove the EGR connector in the closed region and see how the engine performs in all regions with the valve closed . This being a spare for later use .

What is not considered is if the lack of un oxygenated air effecting the fuel ratio where you could burn your valves . This would not be a problem if the ECU maps were shifted at the time the valve is opened in varying amounts .

Just spit balling , not the Engineer .