Last week my 2000 XKR convertible went into failsafe engine mode. Spent all weekend trying to figure out what the problem was. Most of the time was spent trying to get connected to data. Not sure what the issue was. There are a couple things suspect. But due to no communication and turn of events, can't say. First I was thinking something got wet. Now I'm thinking it may have been fuel. I just left the gas station where I put low grade fuel in it. I had always put atleast mid grade usually high octane. But hadn't got my check cashed so figured I'd give it a try. Was about 60 cents cheaper. Anyway I got a couple miles down the road, and it started pouring down rain. Directly after it started missing a bit and failsafe engine mode appeared. Shut it off and restarted. Ran normal for very short time and back into limp mode. Took forever to get home. 2k going up hills doesn't get it. Have had issues with other systems when raining, mainly abs and traction control. I assumed it was wet connectors or something. Had been trying off and on to read codes. It has had check engine light on since I got it a couple months ago. Think my otc 4000e should connect but won't. Now with more reason I was giving some effort. Even bought a new scanner. I also took it to AutoZone and O'Reilly's. Nothing will connect. The one at O'Reilly's recognized the network but couldn't connect. Disconnecting ecm using dvom I verified the circuit is good between obd2 and ecm. Not sure exactly what system this thing uses. Has terminals for k line and canbus. Can't really find much info on this car. Canbus voltage and resistance measures good at obd2 but no continuity between the two lines. Kline measured ok at obd2 also. Something odd, going by diagram downloaded from jagrepair the xk8 and xkr have different ecm with different connectors. Mine has the one it says should be on xk8. This is definitely an XKR. Doesn't make sense because the harness is different. Anyway another possibility on limp mode I had the night before connected the 3 gauge cluster in place of the navigation. While wiggling the wires it came out of limp mode once or twice. I didn't buy the aftermarket harness available. Kinda silly to pay that much for some wires and connector pins when you have them laying around. Did have a bit of trouble finding schematics. I don't think that was the problem. I had only added about 4 or 5 gallons of low grade. So I filled it with high test. To start all was the same. After running it a bit, failsafe engine mode hasn't come back. I'm assuming maybe the fuel caused detonation or something causing the problem. Has anyone else had this problem?

 

I can't see an XKR accepting an ECM from XK8. Can you post a pic of engine and ECM?

 

That's just it. They can't. They have different connectors. Unless I got something mixed up. Manual shows 2 modules AJ27 N/A which I assume is for XK8. And AJ26 SC which I assume is XKR. Mine definitely has AJ27 N/A. And definitely is XKR. It has a 4.0 with supercharger and intercoolers. The information was from page 21 of 1999 Range electrical guide. I could take pictures, but don't think I can post them. Think there are requirements to post which I have not met. I have a xk8 parts car. Was thinking about looking to see what module it has. But haven't gotten around to it. Seeing how they can't interchange, I assumed it was labeled wrong.

 

AJ26 was just the earlier iteration of the jaguar V8. This then became AJ27. The change to AJ27 happened around 2000 for the XKR and several years earlier for N/A motors (N/A is "normally aspirated, ie NOT supercharged). In other words, both XK8 and XKR variations shared both AJ26 and AJ27 motors during their production until the change to 4.2 motor.
I think the reason for your confusion is the fact you are referring to a 1999 diagram. The supercharged cars did not move to AJ27 until 2000. These cars were constantly changing and you really need to reference the correct info for your model year. Download the 2000MY guide. Fig 4.4 and 4.6 for your engine management.
As to your original problem, l suspect it may have been due to the low octane and knock sensors detecting what you did not.

 

The issue could also have been caused by moisture getting into the throttle body....

 

Thank you for the information. I figured n/a was for naturally aspirated, and SC was for supercharged. That's why I assumed I may have the wrong ecm. Was also thinking the fuel had caused the problem. Hasn't given me any problems since putting high octane in it. I tried to get the 2000 manual but couldn't locate it. I did find it listed somewhere, may have been this site, but when it either wouldn't download or downloaded the wrong thing. I had both happen( on 2 different sites) but don't remember which happened on which site.Would really like to have the correct one. Would love to have a shop manual with a bit more information in it. Something that gives a description of what the various electrical systems consist of. Would make it easier to know where to go with figuring out the data connection. Apparently there are groups of modules communicating on different protocols. Obd2 has Kline and canbus wires. Would be great to know what's on what. It's running good right now. But it has check engine light on. Also throttle response is a bit slow. And I know it not ever going to have good fuel economy, but seems a bit thirsty. I figure the economy is due to my foot.

 

I looked at throttle body. It seemed to be fine. Was slightly dirty. I cleaned it and checked tp connector. Nothing changed. Also cleaned maf sensor, checked for vacuum leaks. I'm pretty sure it was the fuel. Just can't prove it.Havent had any problems since putting high octane fuel in it. However, it still has check engine light on as it has since I got it. Need to get connected to the data.

 

I saw you had a post on front strut mounts. Did you ever come up with anything good with that. The guy I got this from says he replaced them. I have to look a bit closer. They do look like they might have been. But the left side strut rod may be a bit off center. Tires are wearing very badly on inside edge. And it sits about inch and a half low. It may have lowering springs also. The springs on the xk8 had one more coil. Might just be the front crossmember mounts . They definitely need replaced.

 

Try member Gus' site of everything:
http://www.jagrepair.com/images/Auto.../jagxk2000.pdf

 

Thank you. That should help tremendously. I tried to find it on that site and failed. Saw it listed, but couldn't access it.