Hello there!

We have our mate's lovely 1999 XJ8 Sovereign that came in to have its chassis rails repaired -- the parts where the engine bolts/mounts to were too rusty to continue driving this good old girl.

All this meant engine+gearbox had to be dropped, and the reinforcement/repair welded into the rails.

The battery has been kept disconnected during the work, when finally the engine+gearbox went back in, all cables/looms/connectors plugged back, we reconnected the battery, and the whole instrument cluster lit up with faults even without having to put the key in ignition.

We realised it was the inertia fuel cut-off switch that probably gotten tripped during welding/bashing. We press-reset that, and then the dash was no longer lighting up - things were looking better until...

...we turned the key on to the ignition "ON" position: same errors came up, and the car would not crank, the starter would not even try to..

I have read your famous all-helping thread No start: gearbox fault incorrect part fitted but before I delve into the world of wiring diagrams, maybe you could point me out in simpler words as to where to check first.

The faults on the display scroll through (as much as I can remember):
Low brake low (we haven't filled the brake system up yet)
Engine coolant low (we haven't filled the cooling system up yet)
Traction control fail
Stability control fail
Gearbox fault
Failsafe engine mode
Incorrect part fitted
Centre console initially beeps and is showing "Er"

The battery charge was quite low (11.8V), I then have additionally plugged a RoadStart booster jumper, bringing the voltage to 12.4V. All the faults are still present.

A scanner (SnapOn, meaning it probably won't show genuine Jaguar codes) has been plugged into the OBD port, and managed to talk to the Transmission Control Module, which keeps bringing up P1797 "CAN transmission control module to engine control module malfunction"

Communication with the Engine Control Module would keep on failing (with battery charge 11.6-11.8V), but we'll try again tomorrow with the battery being 12.4V.

We've checked most of the fuse-boxes, all fuses were intact. We'll complete the checks ASAP, I just wanted to run this thread in parallel to our effort, to hopefully get somewhere in the end

It is very astounding to simply take the engine+gearbox out, fix the chassis, put them back in, carefully reconnect everything back together (and double-triple-check all the connectors, including false-bulkhead starter mains cable), and then be greeted by this scroll-of-death...


I hope you fellows could see us through in this maze!


Many many thanks!
Jagsim

 

The battery being above 12v (nominally 12.5+) is important and I would do a reset (disconnect the battery cables, ...touch them together for about 30 seconds and reapply). But be sure the battery is up to snuff first. No corrosion at all on the cabling or just replace them then. Double check the grounds also.
Its those seemingly unmoved things that go awry when we find out they did get moved, at some point, some how.

You'll want to bookmark this if you don't have it... JagRepair.com - Jaguar Repair Information Resource ...plenty of useful info and diagram details. Such as this DTC list... http://www.jagrepair.com/images/Auto...J27%201999.pdf

 

Just hooking a battery back up after a while can blow fuses, so check every one.
The battery needs to be at least 12.5V before you can be sure it's not a low voltage fault. You should be able to OBD with a properly charged battery.
Earths are also a good thing to quadruple check, the battery ground strap can be a culprit, along with the engine earth underneath.
See what it reports with a decent charge and reset.

 

Many thanks to your answers!

Problem FIXED! ECM (and CAN bus) either sorted themselves out given some time (~20mins), or CAN bus has "cleared" itself after I have turned the radio on (and Enter Code screen appeared) - I've never tried to turn radio since the engine went back on.
I did not have a code to hand, but I didn't need it -- soon after there was an "alive" noise in the engine bay, and it cranked!!! All related errors have been cleared and are now gone for good. So chuffed and happy, lost for words!


Thanks!
Jagsim

 

These cars are VERY sensitive to battery issues. A less then perfect battery can do the weirdest stuff. Glad yours worked again. I can feel your sigh of relief through the screen.