So ive had transmission issues on my 04 xjr for years now..Ever since I blew the original up and installed a slightly used unit. The first unit slipped and I couldn't program the TCU even though it was supposedly from the correct VIN car. I swapped TCU's and it was working but slipping in first every so often and doing a strange lock unlock of the converter. I did have the memory cleared at one point. This led me to a second transmission install. SAME ISSUE....So I basically returned my car to stock minus exhaust and intake mods and dealt with it.

I would still drive it but I was not enjoying it. Always worrying that the transmission would just give. I had everything tested that I couldn't do myself and no one could figure it out.

To top it off I had a small coolant leak develop in which I could smell the coolant but not see where it was coming from...So smelly bad running 2004 XJR..Fine, I have other jaguars! I put my Cayenne Turbo into daily driver mode.

One thing I was noticing when I drove also was that every so often it would go into limp mode and Id just reset and continue to drive it was a TPS error.
It got worse and worse to where I just couldn't take it anywhere because resetting wouldn't do it.

So about a month ago I said screw this. I'm changing the TPS and while I'm at it find that coolant leak. Seems you can get new TPS now....Well...…While I'm at it

1) Various vacuum lines and fittings were replaced. The bushing in the SC inlet was shot as well
2) Various coolant lines replaced Including valley hose which didn't appear bad but....
3) New Water Pump/Thermostat(the plastic bushing in the original was like mush but blades seemed ok. Radiator outlet plastic was also mushy....
4) Bosch 010 IC pump upgrade. Mine was barely working.
5) All tensioner/idler pulleys. (Hey a squeak went away!)
6) Two belts, they were cracked and original
7) SC synthetic fluid change and solid coupler just because(Its actually quieter)
8) New TPS(UGG)
9) New Coolant level sensor(still not working)
10) Resealed cabin filter plastics with foam rubber

Upon completion I start the car its running like crap. TPS bank B low voltage code...WWHHAAATTTTTT@!!!!!!!!. So I pull the TB and install the one from my Maxbore TB that I pulled off awhile back.
Start car back up. Idles like a kitten. Hmmm..I don't recall it idling this smooth in awhile. I drive it around, to the store (lose my phone in the process) and the transmission isn't slipping.
As a matter of fact there is no converter lockup craziness going on either...Too good to be true. So I decide to take it to work a few days. NYC to Bridgeport CT and back a few times, a few runs throughout NYC.
Runs better than it has in a long time. Almost like when I first got it.

So. My question is this. Is there ANYWAY he TPS could have caused my transmission to work improperly? Seems plausible...Or could it be the battery being disconnected for a month?

ALSO. are there any good aftermarket TPS. Seems hit or miss
And the coolant level sensor. The old one worked intermittently. When I pulled it out it didn't have a plastic sleeve like the new one. Could that plastic sleeve have been to protect the element only from damage only. I didn't remove it and now it doesn't work at all. Im guess for those that have changed theres maybe someone has an answer...

Anyway...I'm unbelievably happy. I know it didn't just fix itself but something fixed it!

 

Hi XxSlowpokexX,

Thanks for the detailed update!

I think the short answer to your question is yes, there is a very high likelihood that the TPS is directly involved in transmission management. Here's what the Technical Introduction has to say about transmission control, from pdf page 102:



It does not make clear whether the throttle pedal position signal comes from the Accelerator Pedal Position (APP) sensor, or from the Throttle Position Sensor (TPS), or a combination of the two, transmitted from the ECM to the TCM via the CAN, but given the symptoms others have reported that have been rectified by replacing the TPS, it seems likely that your TPS has been part of the problem.

You can download the Technical Introduction Guide here:

Jaguar X350 Technical Introduction


Off the top of my head, I think the new ones I've installed have had a very thin plastic tube like a drinking straw over the sensor element, which is a reed switch. But on many of the cars I've serviced, that cover is gone and the reed switch is exposed. But that shouldn't make a difference because the reed switch fits up into a closed cylindrical recess molded into the underside of the reservoir and should never make contact with the coolant. Inside the reservoir, a float with a magnet attached rises and falls with coolant level, and when it falls too far, it slides over the reed switch and the magnetic field causes the reed switch to close, completing the circuit and triggering the Engine Coolant Low warning lamp. Here's a link to a document that explains how the sensor works:

Littlefuse Reed Switch Coolant Level Sensor

And here's a video:


One thing I've discovered while troubleshooting the X350 coolant level sensors is that the signal passes through at least two electrical connectors on its way to the instrument cluster. There is a smaller connector down below the reservoir near the radiator and intercooler pump that you can follow the sensor wire to, and a larger connector at the base of the right A-pillar. I can't recall for certain, but it may also pass through a larger connector near the right side suspension tower. I remember that cleaning and re-seating those connectors resolved some issues on a car that had a persistent low coolant warning. Check the Electrical Guide for the connector locations:

Jaguar X350 Electrical Guide 2004

Cheers,

Don

 

The underlying thing is that if the engine isn't quite running right it can cause tiny jerks which then upset the trans.

So, many time a trans fault is actually a big hint that the engine isn't running as well as you may think.

(And if you have codes, fix 'em!)

 

The TPS was intermittent until it was awful. But trans issue occurred more often. Drove another 100 miles no issues. About the coolant sensor. Maybe I disconnected the other wire Ill need to check...OR the magnetic float is no longer floating. I didn't purge the overflow tank. Maybe that's it. If not....New tank it is!

Thanks!