Hi again. I have read a couple posts about replacing tranny fluids and am wondering - if I get an OBDII scan tool that reads transmission temperature - does anyone know if, in fact, my 1999 Jaguar XJR S/C has a built in temperature sensor? I will apologize in advance if this question has been asked and answered... I am trying to navigate my way around the forums, but find my brain begins to hurt and vision begins to blur. Any help greatly appreciated. Thanks

 

It does have a transmission fluid temp sensor. What you need is an OBD II reader that can display live data and not just one that says it can read transmission temp. Those won't work on our older Jags. Once you find a reader that can handle live data, you'll go into the live data section, put the car in reverse or drive, and it will display the tranny fluid temp. If you're in Park or neutral, it will display engine coolant temp instead of the transmission fluid temp. I don't recall exactly why that is, but it's not a defect, it's just the way Jaguar does it (or did it back then anyway, it's a car-thing, not a reader-thing). I tried a couple of cheaper OBD II readers that said they could read transmission temp, but I learned that what I needed was a reader that could display live data. I ended up buying an Autel MX-808 , and I think it cost me $400 at the time. I'm sure there are cheaper readers capable of displaying live data, and I fully admit to not being educated enough about them, but I can say that the Autel unit works perfectly to read the transmission temp, as well as all the other control modules in the car.

Edit: on the Autel unit, you tap on the TCM module, and then tap Live Data. It's pretty simple, but LIVE DATA is the key to reading the transmission fluid temp!

 

Thank you very much for ALL the info! I was just about to pull the trigger and get one of those Icarsoft LR V2.0 ones... will hold off and look around for an Autel or similar. I really appreciate it.

 

Hopefully you'll find a cheaper reader that provides the live data feature. I tried two local shops first, but they just kinda looked at me funny when I told them it's a 98 Jaguar XJR. That's why I decided to educate myself and buy my own reader.

I don't know how important this is, but the reader has icons for every manufacturer, so you go in and click on what car you have, year, trim level, engine, etc, and then click on the TCM and choose Live Data. My 98 XJR is a little too old for the Autel to automatically read all of that so I had to select it manually. I've used the Autel on two other vehicles of mine and a friend's older BMW Z4 that required a firmware update. It executed the update fine and seems to work perfectly every time I use it.

 

I know that NOBODY reads the TSBs but be warned about reading the gearbox temp on the CAN bus!!!!

A 'non-contact' laser thermometer aimed at the gearbox OUTLET cooling pipe will also be a good temp indication without relying on the thermister in the gearbox internal harness.
Too many mechanics were 'fooled' by the temp reading source.(ENGINE not gearbox)

 

Yes, as I mentioned, the shifter must be in reverse or drive in order to display the transmission fluid temp. The reader that I have shows the engine coolant temp a few lines above the transmission fluid temp. The readings are identical when the car is in Park. Move the lever to Drive, and the tranny temp line instantly changes, which is how I felt confident I was doing it right. If you’re careful and remember to shift it to drive (or reverse), it should give you the tranny temp reading you’re after.