I'm in the middle of changing the internal wire harness on my 99 XJ8. I've been doing searches on this issue for a couple of months and decided to change the trans fluid and filter and internal wire harness all at the same time. So to this point I've dropped the pan and filter and before I go any further I'd like to see if anyone can help with a couple of questions.

1. To get to the area where the internal harness connects to the external harness do I need to remove the valve body on the transmission?
2. If so, how should I do it so I don't have springs and ball bearings flying all over?
3. There is a connector on the harness that plugs into a small black probe thing and then slides into the transmission and is held in by a clip. This is located at the furthermost rearward point of the transmission. What is that black probe and should it be replaced also?

Any guidance would be appreciated.

Thanks

 

A picture of the connector for question 3. It's the connector at the very top of the pic.

 

Sorry, I haven't been there yet so am no help. I would like to know what led you to make this repair.

 

No worries, I'm hoping one of the tech's see's the post and offers a response.

Why would I do it? Well...My Jag has 95,000 miles and I've had it since about 80,000 so I figured it could use a tranny fluid change as I had no idea if it had been done or not but the biggest reason is I'm getting RP and CEL. Not all the time, it only happens when I start the car when it's almost all the way cooled down. So when I start it cold it runs perfect with no RP or CEL. Then if I turn it off and let it cool a couple of hours it will go into RP. But if I let it cool all the way down it's fine. Also I get a "transmission high temp" warning and the codes from the autozone scan tool suggested the temp sensor was bad. I forget the actual code but I can probably find it I wrote it down somewhere. Also if I keep driving the RP clears up and goes away and it runs great. My Jag guy in AZ suggested that the internal harness/sensor does go bad and thought I might have a problem with mine.

 

I have replaced dozenes of gearbox harnesses for the 'high temp sensor fault' and you don't need to remove anything except the fluid, pan, filter, harness and plug assy with 'O'ring. The clip and plug are tricky to reach but take your time and get the plug seated correctly through the case. The solenoid/sensor harness plugs are lined up in the correct sequence so you won't get them wrong.

bob gauff

 

Awesome thank you! Do you know if I should replace the black probe the rearmost connector connects to?

 

Bob, I can't thank you enough. Without your post I probably would have continued to remove things until I had more room. But I didn't need it just like you said. Once I figured out I needed to unplug the external plug first it was pretty easy. It's all done and on the road and so far seems to have fixed the problem. I'll add some pictures later just to help the next guy

Thanks again!

 

Thats strikes me as a strange thing to need replacement - interesting.


What fails?

 

I guess the temp sensor is in the harness and when it goes bad it gives false readings and causes the car to go into rp.

 

Well I managed to screw this up. I'm sick about it. Everything went pretty good but now the trans shifts like crap. Hard 1st to second shift every time. It's making noise and in general not right. Before I did this the tranny shifted smooth when driving normal and firm when driving fast. I'm wondering if It's possible that I got the internal harness Clocked wrong?

Thanks

 

Just to update and close out this thread.

1. My car is and has been running perfect since I last posted. The wire harness was in just fine. The shifting problem was because I used an Amsoil tranny fluid that they said was compatible. Well it wasn't at all. At my wits end I decided to do another drain and refill with a truly compatible fluid from the VW dealer. It's honey brown like the fluid that was in the transmission originally. After one change the car shifted better, after two drain and refills it was even better so I continued to do that same procedure a total of 5 times and I think at this point I have almost all if not all of the amsoil fluid out of there. The Amsoil trans fluid was a much heavier viscosity than the original fluid and the car shifted like the transmission was done. The VW fluid was very thin just like the original Jaguar fluid. The Car drives and shifts smooth as new and has for the last 5000 miles. Lesson learned=Don't cheap out on the fluid!!
2. I replaced an ignition coil at the same time I changed the harness. I was getting multiple error codes before I changed the coil and internal harness including PO300 #4, P1313, P1316, PO354 to name a few. Also I was getting the Restricted performance message and a rough running engine whenever the car got warm. I also got the "Transmission high Temp" warning.
The car was barely drivable but never stranded me and didn't always act up. I was pretty depressed and was seriously considering dumping the car. I'm sure glad I didn't. Less than $500 in materials and a little time in the garage and I have a perfect XJ again. Lesson Learned= one or two small issues can cause a host of phantom error codes on cars with a bunch of sensors.

Anyway for those of you having problems please hang in there. There is hope if you just do a little research and ask a couple of questions.

A big thanks to those that have helped me on here. The time you've taken to respond has really helped and is appreciated.