Last week I found that the OBD2 was not able to communicate with my car. I ordered a used instrument cluster in effrot to correct this issue, it arrived today. I installed it and nothing is different. so is it time for a new ECU/rebuild? I do know the ECU has been changed, infact I got two others with the car. If im going to get it rebuild I'd like to have the factory ECU back in the car... IS there anything else to check before spending 600 bucks to help the OBD2 communicate? or is it time to break out the wallet? and how might I tell which computer is the "right" one.

 

Even if changed, it should communicate. Chances are you have some basic wiring/fuse/etc fault.

 

2 other ECU's came with the vehicle!

Does this indicate it has unresolved module 'history' which you are trying to fix rather than being a new fault suddenly developed on a previously correctly functioning vehicle?

Graham

 

Yes, I bought the car not running and no history... starting from scratch trying to work through it.
here's the rest of the story...

https://www.jaguarforums.com/forum/x...8-198k-115309/
https://www.jaguarforums.com/forum/x...p-fuse-115361/

 

The VCATS label in the luggage compartment lists the serial numbers of the modules originally fitted to the vehicle. It's behind the carpet next to the battery:



From this you can work out which modules are original and which have been replaced. If you do have to have one or more rebuilt, preferable to go with the original matched ones.

When you say "OBD2 was not able to communicate with my car" do you mean the DLC (Diagnostic Link Connector) is dead?

Graham

 

When I connect my scanner, it says it cant establish communication. So yes it's "Dead"

 

Both DLC fuses OK and your scantool known to work on XK8/XKR?


(click on the image to enlarge it)

Graham

 

All fuses in that pannel are good and I veriffied voltage.
Scanner is an Innova 3100 several people on this board have the same and are getting results with it.
as far as the vcats sticker if it was ever there it has been removed... sorry to say my car has 200k on it, I'm afraid the last few year it was most likely not treated very well (4 previous owners in the last 3 years)... I'm hoping to undo that.

 

Maybe meter the wiring at least from DLC to PCM connector? Another cause of failure to communicate can be a module that's bad thus hanging the related wire(s) so do as many tests / unplug modules as you can. But go with any ideas Graham has...

 

I think I found the problem....

 

That removes all doubt - definitely not a rebuild candidate!

Any Jaguar Dealer can print off the original factory build sheet from the Direct Dealer Warranty System. This has all the info which would have been on the VCATS label.

Dealers in the UK are usually quite co-operative with such requests for information but I know from posts on the forum US Dealers have what can only be described as a bizarre approach to customer service and may not be so helpful.

With either of you spare modules plugged in, is there any sign of life in the DLC?

Graham

 

Horrors! Got a water leak, cowl maybe? Is it now fixed?

 

That was one of the replacement ECM's that came with the car...3 of them.
It was installed.. but not the factory one. I not necessarily a leak in MY car but it was definite water damage. I have opened the other two and the one I believe is the OE has a leaking capacitor, no visible damage to the third. I'm going to pop the last one in and see if it will communicate with my OBD2. but it's currently raining.

 

Okay,
I installed the "spare" ECM still no communication with the OBD scanner.
I'm off tomorrow and Saturday hope it's not raining.

 

I sent my ECU to ASI and they did a great job.

 

Doesn't the ECU have to be formally coded to the car? My understanding is that if this isn't done a new ECU won't work. Some kind of a security feature.

 

That is my understanding as well, however even if it was wrong it SHOULD allow the high speed network to function and that is not happening now.

 

Yes, should have OBD comms. (And then codes for anti-theft etc.)

There again, when as bad as that damaged one it might allow/prevent just about anything

 

For good measure today I decided to pop in ECM number 3 (remember my car came with 2 extras) and I KNOW this one has a bad capacitor that has leaked on the board. I figured how much more damage could I do. When I reconnected the battery the fule pump powered up the throttle body woke up and the OBD2 scanner talked to the car. It actually even fired and had there been gas in the tank I believe it would have fired up.

I even got some codes out out of it...
p1638
p1642
p1000
p1637
p1643

 

P1000 OBD Systems Readiness Test Not Complete
P1637 CAN Link ECM/ABS Control Module Circuit/Network
P1638 CAN Link ECM/INSTM Circuit/Network
P1642 CAN Link Circuit
P1643 CAN Link Engine Control Module/Transmission Control Module Circuit/Network

Looks to me like it's saying the CAN is screwed.

But it is doing more now that it has since I got the car.