Things have been good for quite a while in the 2004 XJR up until last week. When slowing down to a stop, as the trans down shifts through the gears, the gear changes became less smooth. If i slow down and Almost come to a full stop but continue to roll it Gets jerky. It tends to do this especially in a slow rolling traffic jam scenario where it seems to be hunting for a gear or cant decide weather to down shift or up shift. At this point it will display gearbox fault and will Hold one gear... I found that if i pull over, shut down the engine and restart the car the message goes away and everything returns to normal.

I have called the Shreveport Jag dealership and the lady insists that they NEVER do any work on Transmissions and that it is a "lifetime Sealed Unit" I asked her about Reflashing and having the trans flushed since it is Currently at 96k miles. She again said that its a sealed lifetime system and wasn't something they worked on.

Now, Today... i went out and started the car and it revved up a bit higher than usual before returning to normal rpm. A few miles later i was in a parking lot and "Engine System Fault" appeared with a Red light and the engine began to sputter then hold itself at about 1500 RPM regardless of throttle mashing. so i shut it down, restarted and kept the revs at about 2500 with the throttle for about 30 sec and i slowly let off... everything was ok, the message was gone. the Check eng light was on. It did this Again on the way to autozone where i had the car scanned.

Codes are P0121 Throttle Position
P0783 3-4 shift

The Gearbox and Engine Systems messages have Not appeared at the same time, but im guessing the same problem is causing them.

Any Ideas? Im thinking the Dealership might be mistaken because i read aot of threads about flushing high mileage transmission and reflashing etc..

 

Hi Bobby,

You can download the official 2004 Jaguar XJ DTC Summaries manual, which has the definitions and possible causes of all the Diagnostic Trouble Codes:

https://www.google.com/url?sa=t&rct=...03388427,d.cWw

P0121 indicates a problem with the Throttle Position Sensor (TPS) to Engine Control Module (ECM) wiring, either an open circuit (perhaps a connector is loose or a wire broken) or high resistance (perhaps corrosion on the terminals of an electrical connector); or a short circuit to B+ voltage; or failure of the TPS.

P0783 indicates a fault in the ECM torque signal or transmission mechanical failure.

My first impression is that the common point is the electrical connector for the ECM, which is under the cabin microfilter housing in the engine compartment. Leaves and seeds tend to collect in that area and plug a drain tube, allowing water to pool around the connector. It would be worth checking the connector pins for corrosion. To disconnect the connector you will need a 5-point security Torx bit (with a hole in the center, and yes, it only has five points or lobes, unlike standard Torx bits). I ordered an inexpensive set on eBay.

Even without a bit to disconnect the connector, you can check for leaves or other debris covering the drain tube - if you find the drain clogged, you'll know for sure that it's worth checking the connector.

You can download the 2004 XJ Electrical Guide with all the schematics and component locations here:

http://www.jagrepair.com/images/Elec...al%20Guide.pdf


Please keep us informed.

Cheers,

Don

 

That all said, you were also having transmission shift issues and much of the transmission control is in the transmission. Sealed for life is certainly NO LONGER TRUE and fluid change is recommended around 50k miles. Earlier units often had a leak, and fluid could be low. There are fluid and pan filter kits. Takes about 7l to change.
There is also a transmission flash and reset of adaptions that can be done by dealer, or users with SDD an finicky software and adapters. There are also reports that failing ignition coils, old plugs, or faulty ignition filter capacitor can cause issues.
I would check fluid, and TPS connections on the throttle, and the intake air pipe between maf sensor and throttle...

 

Ahh ok I will dig into that tomarow. that would make sense because this engine systems fault happened for the first time today when I had just pulled out of the car wash. I bet It IS plugged up with leaves. ofcourse jag would put sensitive electronics near a water collection point lol hopefully it just needs good cleaning

 

Any engine/fuelling/misfires/air leak/closed loop fault can upset the trans so fix any of those first and see if the trans is then fine.

It's because the trans doesn't like a badly-behaved engine.

 

The reason the tranny likes a happy engine is that the network sends performance signals from the engine to the tranny so it can do its shifts correctly. If the torque is off or the signals garbled, the tranny will set a code.

 

thanks for all the info!
I opened up the filter door and ofcourse it was Full of leaves, the filter was soaked. The drain was Plugged up. I'm going to get some wire mesh and glue or attach it to the underside of the Plastic Grill at the base of the windsheild. This factory design is an Invitation for debris to clog the drain. I was wandering why the passenger footwell was getting wet lol. Appearently the water level rose high enough to spill in through the A/c intake door behind the filter..Since it has all dried out I haven't had any problems with the Engine Fault or Gearbox.
I am still going to check with an independent shop about getting the Trans fluid changed and Flashed just to be safe.
Thanks again

 

and change the sleeve and the filter pan bolts for better ones. There are many threads about how and where to get them from.

 

Catsgame, looking into the same tranny fluid change. Be interested to know what quotes you receive.

so far I have been quote $1200 CDN or approx $925 USD. Just the trans fluid (7L) is $485 CDN or $375 USD. Found a link from our good friends on this forum.

6 Speed oil change kit Jaguar

I will be purchasing the parts and have a shop perform the service.

fabcat