Casually driving on the freeway when I go to accelerate to pass a car and it just makes a wheezing sound as the engine light comes on and says gear fault. Plugged the computer in and read P0735 "Gear 5 ratio incorrect".

I read in another post:
But they were talking about an '01 which I think used a different transmission. (right?) Any other thoughts on what could cause this? Car was running beautifully this morning, almost too well.

This transmission has never really impressed me and I wonder if anyone hates it as much as I do.

 

I'm not sure what would cause that. According to JTIS, that code refers to a ECM issue or Transmission Mechanical Fault. I've attached the PDF that lists all the DTC codes for the 03 S, including the R. I hope it is ok to post it. If not, please someone let me know and take it down.

Oh, yea, and that spring issue is for the Ford 5 speed. You have the ZF 6 speed. Other than goofy shifting, I've not heard of any issues with it. It was used for a couple of years in BMW's before Jaguar got it.

 

P0735 is a generic OBD code, as it starts P0 (note: that's a zero not a letter O). It's rare (very, I think) on an S-Type, so try google for it on other (i.e. any) cars. You do have the ZF 6HP26 as Jeff said.

You may find with other cars that it really IS usually the box, but just possibly there will be some other commonish cause in which case see if that may apply to the jag.

But, make sure you don't have any other DTCs. Also, that your readiness monitors are OK (flagged as complete) and that once warmed up your PCM is going CL (closed loop). Then, check the fuel trims (LTFT plus STFT on each bank) are less than about 10%. On older (but still OBD-II) cars sometimes other issues fool the PCM and/or TCM and bring up an auto fault.

(You won't be able to do all that without at least an entry level scanner.)

Always treat a DTC as a hint not a firm diagnosis.

 

I did receive this code also, but didn't think it was really important:
P1111 - Manufacturer Control Fuel Air Metering

The document JOsworth posted said 2 possible causes:
1. ECM Torque signal fault
2. Transmission mechanical failure

It also said the default action would put it into limp mode, which mine did not do. I also forgot to mention that once I tried to accelerate at Highway speeds and the error happens, the sport mode button no longer turns on. I'm assuming that's just part of the safety limp mode.

 

P1111 does NOT mean that for a jag (or a Ford). If you got that text from a scanner your scanner is deficient.

Being a P1 code, it's manufacturer-defined. For jag/Ford it just shows that the readiness monitor drive cycles have run OK (which is good). You can check by looking up that DTC in jtis (or Ford's free online info).