My X300 always been a bit of a girl, working fine for a while, then randomly misfiring on petrol for a day or two, I just cant please the damn car, it just requires constant attention to work fine, even if its just a quick clean up
I was replacing steering wheel cable today and thought I'd inspect the ECU at the same time, as I've heard and seen some of these water damaged.
First, to get it out, a bracket that holds the two plugs needs to be removed. Of course Jaguar thought to make this as hard as possible and installed special screws to hold it to the ECU! I've ended up cutting them in the middle with an angle grinder so a flat head screwdriver could be used. Got it out and the ECU looked like new, no damage to the sockets, or any signs of water damage but I thought I'd open it up anyway, see what's inside.





I've removed all the screws and pulled the board out and eventually I noticed a clearly burnt out track near where the middle screw is!




Right next to hole, resistor R268. This was clearly damaged during assembly, looks like someone scraped it of the mounting hole and then it probably burnt out!

I've repaired it by adding a piece of small wire



Everything else looks like it just came out of a factory



Just shows that any of these ECUs can be faulty



Quality control = clearly poor!

 

Just so you know, those are just torx screws. You can buy a set of compatible screwdrivers at most any hardware store. Probably better than bringing an angle grinder within 10mm of your ECU!

 

Yes, I'm well aware the ones in the pics are torx although the two that hold the plugs within a bracket on top of the ECU are definitely not torx

Unfortunately don't have a pic of them but Jim Butterworth mentioned them on his website too:

'I really wonder how Jaguar did their fault tracing if they couldn't take the plugs & sockets apart? Presumably they gave the customer a new car if the ECU went faulty ?'

So true

 

Just a quick update to say that I did 1000 miles now after this 'surgery' and the car didn't miss a beat(which would never happen in the past) so I'm pretty sure that all these random idling issues were caused by this factory ECU fault, fixed after 21 years!

 

So... you could tell that one of the tracks from R268 was burned out near the screw in the first picture? And the jumper wire replaces it? Were you able to test the track for continuity first? Could you tell if the resistor was still good or if it was damaged? You have some very fine soldering skills. I would never attempt that on an ECU board. It would be ruined.

The car runs very well now, so good chance that was it! A lucky find that would have been impossible without burn marks or other evidence like you found. Nice work.

 

Yes the track was clearly scraped when someone assembled this ECU in factory and because it was much thinner and damaged it eventually burnt out completely and I've checked for continuity and it just wasn't there hence the extra wire to fix it. Resistor was most likely still fine, comparable to the rest of its size and the car now drives as it should on petrol and lpg(which runs of its own ECU)