I picked up a 96 Xjr on eBay from Florida.
She's running great only 90k
Took it in to smog it today and everything passed except for being able to communicate with the computer.

I noticed I can't use my elm wifi obd reader to see values.says it can't connect.
I have a vcm with Ids on the way but if this doesn't work I doubt that will work too.

Any ideas?

One would think of its not communicating that the engine and everything else wouldn't run.

I'm super bummed about this. As it passed everything to perfect.

 

Those cheap elm obd readers don't like to interface with my XJR either. I have a OBD scanner from Harbor Freight and it reads codes and live data just fine.

 

There's a fuse for the OBDII port in the boot fuse box....sorry, can't remember which one, but do remember it is in the boot box. Anyway...if your elm adapter lights up when you plug it in, that's probably not your problem...but may be worth a check. 15A I *think* but could easily be wrong...

 

great my elm lights up.
idk what else to check.

 

Hmmm... in that case... have you successfully connected your elm to any other cars' obdii?
I've had elm's that won't connect to the phone, some that won't connect to the ecm....think I had 1 that would connect to one of the s-types and nothing else....
It's a crapshoot with the $10 Chinese clones.

 

yes I have. it works on my Range Rover but it won't connect to the smog test equipment either.
I now have a car that I can't drive or register because it can't connect to the damn computer.

I have torn everything apart to see if there's any loose wires or anything.
nothing.

 

"torn everything apart" ? Have you had a good look at the OBD connector pins? How about testing ("ohming out"; I hate that term!) the ODB to ECU wiring? Any water on the ECU connector pins? And you can get a fleabay ecu for less than $200. That might not fix the problem, but it will go a long way towards diagnosis by elimination!

 

just checking for loose wires and whatnot.

I was going to try and test the pins but I can't seek to find where they go in the wiring harness are the electrical diagram.

I was thinking the Ecu route. but it's the xjr and those ones are hard to come by.

 

+13

 

It might be something as simple as damaged pins, or pins that have been pushed back in the connector shell.

The connector has many pins which are defined under the obd-ii standard. Those
can be tested easily. For example the power and ground pins.

 

yep checked the pins.
they are all ok.
I used a multi meter to check to see the pin which is number 7 that goes to the ECU it's an orange wire. and it was ok.
it's so dang odd. you can see it communicating with the ELM "light flashing but it doesn't recognize the OBD connection.
the car runs perfect.

 

I THINK the ECU hardware is the same for the NA and SC ECU (although the TCU is different). The PROMS should have all the configuration on them and they can be swapped from one controller to the other, if that is the case. Maybe motorcarman can chime in here with the facts!

 

I took apart the inside of the ECU and there's a lot going on in there.
from what I can see everything is soldered on.
i'm curious to know where the proms are.
and the supercharged motor has a different compression ratio and fuel injectors I think.
I ordered two xjr Ecus on eBay tonight. I guess will see how that works out.

 

I do not have a module incfront of me, but as I recall, among the large "chips" are two with a label different from the others that are in sockets. You must be EXTREMELY careful removing and installing them and you really should use a puller tool as shown. Check with your older bit head friends.

Have a look at the pdfs in post #4 here: https://www.jaguarforums.com/forum/x...roblems-62255/

 

I didn't see anything in there that looks remotely like sockets.
there were some chips that were standing sideways but they were soldered onto the board.

 

those are great PDFs.
I did notice Those colord blocks the proms are under those!
well @&$! looks like I could've ordered cheaper xj6 ECU's.

 

Well, maybe, maybe not. I re-read bob's post and he said he wasn't sure about hardware differences. If he did not know, then Andy would be the other possible authority on the ability to cross the NA and SC ECUs, I suppose.