My X305 6.0 has an ECU LNA141OEC which seems to be playing up, as it can't be read. the car runs for 5 mins and then cuts out. The part number for the X305 ECU I'm told is either LNA141ONB or LNB141005 can anyone with a X305 6.0 offer some advice please? Much appreciated. Mr Stranded.

 

https://www.jaguarclassicparts.com/u...dule-6-0-litre

I personally do not have any experience with the V12 but others do . You might try posting on the XJS section .See page 193 / 360 if it is a Denso ECU or 261 / 360 if it is Lucas of the V12 manual . If you can , try to determain if the 2 fuel pumps stay on as the engine drops out . What you are looking for is the timing if the pumps turn off before the engine dies from a idle position or if the pumps turn off after the engine dies and falls through to a lower RPM . This can be felt as a thump of the 2 fuel pump relays or as you pull the forward wall carpet down in the trunk the 2 pumps are in the top tank flange . If the engine dies because the pumps turn off at idle you can bypass the ECU control to the ground seeking relays by providing a ground with small wire White / Pink for relay #5 and wire Pink / Black for relay # 7 Ref wiring schematic figure 4.4 . This can be done as a temporary fix by an alligator clip to the car grounding point next to the battery . Leave yourself plenty of wire to work with and not cut too close to the relays and I recommend you put in a service loop . The relay tray slides up and out to work on . If this gets you anywhere we'll look at the rest of the pump control wiring to get you a permanent fix before you purchase a ECU . My one fuel pump control wiring on the inline 6 was messed up by the previous owner so I have tossed that salad in order to get back to the original factory configuration and working properly .

This only addresses a fuel starvation issue for you may have something else going on say a engine control valving or ignition

I am assuming that the V12 is not OBD 2 complaint and would have to maybe revert to OBD 1.0 or 1.5 to see something in the form of a moris code check engine light flashes to give you more information .

The V12 version of the X300 may be the same as on the XJS and since there were not a lot of them made as X300s you may find more assistance on the XJS model section . If the ECU has some form or parts of OBD 2 an ELM327 laptop tool may be of assistance .

Per Wikipedia:

The X305 was equipped with an On-Board Diagnostics System. However, it failed to fully meet the OBD-II specifications, which became mandatory for the 1996 model year in the US. With a special dispensation for that model year expired, no 1997 model year X305 models were sold in North America. In 2001, the United States EPA and Jaguar Cars entered into a settlement which extended the emissions warranty on 1995 and 1996 model year XJ12 sedans to 14 years or 150,000 miles, due to their non-compliant NipponDenso Engine Management System, which was unable to provide continuous misfire monitoring, a requirement for OBDII compliance.[8]

https://www.epa.gov/sites/production...jaguar-asa.pdf

http://www.jagrepair.com/images/Trai...20-%202000.pdf

http://www.mediafire.com/file/fzydrc...300_Manual.rar

http://www.mediafire.com/file/aact8u...ng_Diagram.pdf

 

Lady Penelope, thank you for your comprehensive answer and apologies for not replying sooner, I've just seen your post now. Unfortunately the ECU is now off the car and with me in the UK (the car is in Asia, it was originally supplied to Indonesia and is the LWB model), so I'm not now able to run the check you suggest. I am still struggling to find anyone than can diagnose the ECU..(tried BBA Reman). Will post in the Xjs section as you suggest.
Thank you! Roo.

 

Just my opinion but before you were to spend the money on a ECU , I would look outside that box . You can swap the fuel pump relay or just jump power straight into the pumps by removing the relays or just tap on the existing relays in place before you put it on the road . Someone in the XJ ( S ) section might have better suggestions and help you define or better describe the " event " that may point to the engine regulation sensors or something in the foundation of the engines basic needs like grounds , fuel filter , coil and points on yours and such . How did the RPM dial respond as the engine failed ? Was the dial on zero before the engine ? Battery that open cells as it warms up is an example of foundation . See the linked V12 document as some information : notice the fuel system details on page 206 as you split your engine's issue ( s ) into sections of consideration

http://www.jagrepair.com/images/Trai...20-%202000.pdf

Hope This helps, Parker