Good afternoon all,

I'll try to keep this as short as possible.

On Father's Day, my other otherwise near perfect 1997 XK8 with about 60K suddenly, instantly died whiel at speed. (See my other post "Total everything failure..."). In short, engine, transmission, stability control, incorrect part messages where shown on the display. No OBDII codes. Link failure is the only message on the reader.

On the advice of folks here, I sent the ecu to be tested and, if necessary, refurbished. After almost a month, the company advises that they have been unable to produce a hardware failure on the ecu. Since there were no codes, they are having to check each connection. But, so far, nothing. He said it could be the software, which his company cannot fix.

The gentleman suggested that I could check each wire on the car for signs of a power loss or ground issue using a pin out check (I think that is what he said). Or, I could buy a replacement ecu. I believe the price is close to $1,500, but there is no guarantee that it is not a car grounding or other issue. By the way, I would gladly spend the $1,500 if I knew that would solve the problem, although he said the replacement ecu would have to be reprogrammed using special equipment that I do not own.

I am not sure I have the expertise to check the wiring, power, grounds, etc.(car electrics are a real weakness for me). I have already checked inertia switches and, I think, the relevant fuses. If there are suggestions for specific fuse checks, I am, of course, game for a recheck. If there are specific grounds or power source connections, I will check those as well.

The car is in my garage and, obviously, not driveable. Again, I do not mind spending money on a known fix, but I am not likely willing to have a garage begin to check unknowns at $100 per hour.

So, in a nutshell, it is a very sad tale and not one that I have been able to replicate on this forum.

Thoughts, advice?

Thanks.

Madbrad

 

The first thing I would do is put the ECU back in, clean the contacts on the connectors and see if the problem still exists. I assume the battery is still disconnected, which will provide a reset, and fully charged.

Who tested the ECU?

 

Agreed. Try the original ECU again once it is back in your hands. You might just get lucky....

And as always, make sure your battery is Team-of-Clydesdales strong....

 

If it doesn't work and you can't do simple DIY electrical stuff you'll need someone who can.

 

iirc from the other thread, it looks as if there is an issue with the CAN bus as the instrument cluster isn't able to reach the ECU amongst others, which can be caused by the inertia switch (which it isn't if you checked it), or by a failure of another component on the CAN bus (example gear selector).

So you need to find someone that can check the resistance values of the can bus (between all units), that would be a 1st imo. I don't know by heart what these values are, I think 60 or 120 oms or so, it is documented either in the jtis or on the electrical guides.

 

That sucks that ASI couldn't find anything wrong with the ECU, I was hoping thats all it would be and you'd be back on the road by now.
My first thought though was a CAN bus problem of some sort as that could cause the multitude of problems you are seeing. The CAN bus goes to all the modules so with a good wiring diagram it can be checked out with an ohm meter. It could also be a ground or power problem at one or more of the modules. I would also use a wiring diagram and check for power and ground at each module. This could all be caused by a connector somewhere not making good contact. Or even a fuse socket not making a good connection.


Dave

 

Thanks. I have asked to have the ecu returned, since apparently it was not at fault. ASI did the testing and I have no problem with the service they provided. (I was actually hoping that it was the ecu to resolve the problem.)

Anyway, I seem to back at square 1. I will re-plug the unit once it is returned, clean the contacts, and make sure the battery has a great charge.

Thanks again.

 

[QUOTE=avos;1272121]iirc from the other thread, it looks as if there is an issue with the CAN bus as the instrument cluster isn't able to reach the ECU amongst others, which can be caused by the inertia switch (which it isn't if you checked it),

Does it help that all gauges in the instrument cluster and center console are working/registering?

"or by a failure of another component on the CAN bus (example gear selector)."

I do remember that I had a short lived issue with moving the gear selector out of Park on one or two occasions. And now, to move it of Park, I have to insert a screw driver ( I removed the torx screw) to select the gear. Plus the lights were flickering on he gear selector after the incident. Something relatively simple that I can check there?

 

That could be a problem with the shift cable or the switches that are activated by moving the shift lever. They are in a box and are activated by a cam of sorts. The cable has to be adjusted properly so the shifter and switches are in sync. But a power or ground problem could cause some flakiness there also.


Dave

 

In my attempt to be productive while I wait for the return of my ECU, I took a look at the ecu wiring. I noticed a plug that appears to have no connection. Just wondering if anyone knows what it is for.