Hi all, so my x-type has been standing over a long period of time since the beginning of Covid basically and now I am struggling to use the car in "D" mode. Reverse, 2,3 and 4 all seem fine. The issue I have is that when I put the vehicle into D mode, it doesn't seem to engage the gears and just revs like it is in neutral. I had the codes read and it came up with a "P1780 D - 4 switch circuit malfunction" but when I cleared the code that fault didn't seem to re-appear (it might have been linked to the dead battery I also had). Can anyone kindly advise what could be at fault here ? I believe these gearboxes are sealed units so shouldn't need fluid renewal but I am not 100% certain. Thanks

 

Hi Willow5,

Not my strong suit as I haven't had to go into this problem on my car, but I have some initial ideas for you to check, and perhaps another member might be able to add their thoughts later to assist as well.
What is the year of manufacture for your car?
Are you getting the 'D' light illuminating on the J-Gate when you do select drive?
I assume you are getting other selection lights for R, 2, 3 and 4 illuminating appropriately.

A sitting vehicle, one would hope this is just a simple mechanical issue.....like the J-Gate cable selector to transmission binding (needing some new lube) or perhaps just slightly out of adjustment.
We do get some bad earths from time to time on our cars, so it could be worth checking the earth points for both the TCM (transmission control module) and the J-Gate to make sure the lug and landing mating surfaces are clean and corrosion free.
There is obviously a positional switch in the transmission (I don't have that same transmission in my variant). It is hopefully less likely that you have an issue with that.

Start with making sure the transmission selector cable and J-Gate along with the transmission selector lever on the gearbox are all working smoothly....something might have sulked with the extended sitting period.
I have seen other members talking about selector cables becoming sticky due to aged lubrication.

 

Hello Mark

Thank you for your reply. Here are some responses to your questions:

• I am getting the 'D' light on the J-Gate
• Other selection lights for the other gears are illuminating properly
• The problem seems to be intermittent as the other day when I selected 'D' I got the D engaging
• Please can you kindly explain where the earth points that should be checked are located ?
• Where is the J-Gate cable selector located (top or bottom of the transmission?

Thank you for your help

 

There are two threads below that might be of assistance for location of cable and some discussions on similar troubles.
https://www.jaguarforums.com/forum/x...t-bolt-206933/
https://www.jaguarforums.com/forum/x...-fault-206869/

As for earthing points, here are the locations of the relevant three.