When I started my 2.1 Xtype 2003 model, and selected reverse (automatic gearbox) the battery light, plus an orange light plus a sign came up on my dash to say that there is a “gearbox fault” plus the engine service light also lit up. Now, as I had to get home, I drove it, albeit, rather slowly, but once home I switched off the engine & switched it back on, only to discover that EVERYTHING was working as it should. The warning message re. my gearbox was no longer there, my rev counter and temperature gauge were working,? So I took it for a short drive and it drove perfect. Could someone tell me, WHAT JUST HAPPENED & will it happen again ?

 

Hi Docko,
Sorry to hear you had that scare.
Sounds very unusual.

You referred that the rev counter and temp gauge were working after you restarted engine.....does that mean they weren't working when you had the fault first emerge?
Anything unusual about that initial shift into reverse from park when the error first showed up?
Did the transmission change gears normally while you drove home carefully, or was it harsh in its gear changes?
Was the throttle behavior normal or were you noticing a gap in response when you started to apply the accelerator?

 

“Gearbox Fault Notice on Dashboard”
Firstly, thank you for your interest and reply.
In answer to your questions,,, Once I began to reverse from the parking position, the battery light (ignition light) came on, the temperature gauge and the rev counter ceased to work. There was no noticeable change as I selected reverse gear position on the automatic gearbox, but, as I was driving forward, it was as if the clutch was slipping on a manual geared car. It also had that feeling of trying to drive off while in TOP gear, but once I got going, the gears NEVER CHANGED. However, the engine was reving very high, so I brought down the revs by lifting my foot from the pedal. There always seems to be a lot of traffic behind you when something like this happens as you’re driving. But someone suggested it could be the battery, so a friend of mine checked it this morning with some sort of gauge/meter, and according to him, everything is sound. So It’s back to the drawing board for me.

 

Mine used to do something similar whenever it was really pouring. In my case, water was getting into the computer and throwing lots of crazy errors.

 

Well I can tell you, it’s been lashing rain for a week now, so it might just be that. So how does one protect the computer from the rain ?

 

https://m.youtube.com/watch?v=gY0SHHCl3DE

 

Do you happen to have damp front carpets - right front foot well?

 

I didn’t notice, but I’ll certainly check tomorrow morning. I did leave (by accident) the passenger side window open two weeks ago and it rained all night long, so that could be the beginning of my problem ???
my oh! My, but they really are a temperamental car, compared to the cars of yesteryear ?

 

It's getting in through the engine compartment. Originally my dad fixed it (he had the car for several years while I was abroad) by putting some vinyl tape down along the bottom edge of the window, but it was an imperfect solution. I'll ask him what he did that actually solved it and report back.

 

If the carpet is wet, it may be that water came through the cabin filter intake, down into the heater and can then drip down behind the J Gate selector onto the wiring loom that attaches to the transmission control module.
It is normally well sealed but moisture can find its way through the plug in small quantity and create some corrosion inside module that can cause some issues eventually.

I had a similar failure of lack or odd gear changes, occasionally hanging and then rough and harsh reluctant changes. Then gearbox light would eventually come on, and I did end up with engine light.
My issue was the TPS sensor failing....I eventually found a replacement third party sensor assembly rather than the whole throttle body which is the normal minimum part.

If the problem persists for you, check the TCM module (open it up and look for any green/white corrosion growing on internal connector legs), perhaps change your TPS as it is relatively cheap (under $100 including freight) and easy to do.
You can use a Walker Products sensor, part# 200-1060

 

From my dad:

"Well I found a post in Britain that showed the location of the transmission computer on the drivers side of the car and the explained that the leak was thought the rubber grommets. So I took off the window wipers, removed the covering under the wipers and then found the grommet and used aluminum sided duct tape and carefully started to put duct tape around the grommet much like a roof Is done. Put the outer most layer around the wire and the grommet. It is important that the wire to grommet is done well first by putting half of tape on wire and half on grommet, then putting more tape on wire and overlapping the tape till it just reaches the start of the grommet. Then putting tape , overlapping the tape on the grommet towards the firewall . Make sure tape is completely Around the wire , grommet , and where grommet connects to firewall. By the way the computer and grommet needs to be dry and working before one does this or the water will be sealed in. Very bad."

 

My Lord, This sounds way too difficult for me to handle, especially as I don’t know what a TCN, or a TSC are. Now I’m 78 years of age with Parkinson’s, so I think I’ll pass the information onto my son, and maybe he could tackle it for me. I just got a thought however,,, If I put a hairdryer on the floor of the car, and turn it onto, HEAT, would that dry out the computer? because, you lost me when you said, “remove the wipers” 😂🤣😂
Maybe Jaguar had a recall and they could fix it ? . I somehow doubt it, especially as the car is a 2003 model. But I wish to sincerely thank you all for your valued information, and assistance in trying to solve my ongoing problem. Thank you, one and all.
Regards, Docko. 👍

 

I’m sorry, that should read, TPS,,, and not a TSC… What chance have I at repairing my problem 🤣😂🤣

 

TPS = throttle position sensor
TCM = transmission control module

Heed the TCM posts, main problem, others are less likely =

https://www.jaguarforums.com/forum/x...t-14563/page2/
My video link above shows where and how to fix

 

Well now, as I’ve still got my “gearbox fault” notification showing on my dashboard, the problem still exists. However, what’s happening now is. When I start the car for the first time, everything is working perfectly. I drive to the shopping centre, do my shopping and jump back in the car to drive home, BUT, now when I start it, the dreaded gearbox fault sign comes up, the temperature gauge doesn’t work, and neither does the rev counter. Then the Engine Service light comes on, plus some other dash lights I’ve not seen before come on, including the ignition light,,, but the engine is running? I drive off, however, I seem to be locked in TOP GEAR, as it’s taking everything that the 2.1 petrol engine can give, to drive away ?
on this Friday, I’ll be at my sons house for Christmas Day and he’s going to lug in his electronic machine to tell me the codes, so as it’s of little or no value to me to know them, I’m hoping that there’s someone out there who will know what to do, so my problem goes away…
In the meantime, I wish you all a very happy Christmas, and a safe and successful 2022. 🤓👍🤓

 

From what you are describing, the car is going into "limp home mode" which restricts engine power and revs when the error lights come on.
It still sounds like you have a data communications error somewhere that is stopping the gearbox control module from talking to the engine management computer and the instrument console.
It will be interesting to see what error codes your son can see.

 

I have had the same issue many times and I am almost certain that it's due to rain water collecting on top of your ECU harness plug, which is located on your firewall on the right side of the car. If it gets into your passenger compartment, it will travel down your heater blower motor and collect in a neoprene cover that just hangs under the passenger side door well, under the blower, and once that fills up it will drain onto your floor, and soak your carpet. I've also heard of water getting into the LEFT foot well, and affecting the AT module, but I'm not sure that was the problem in my case. Also, I've read that the heater instrument cluster will have problems communicating with the ECU, causing the Gearbox Fault. And one final bit of advice, IF it happens again, do NOT put your car in Park or turn the ignition off. If you put it into Park, it locks in that position, making any further movement impossible, and if you turn the ignition off, you will not be able to start it again, it won't even crank. So if it happens, just continue to "limp" home where you can park it and leave it be and after a period of time, could be immediately or could be hours, you will eventually be able to start it again without any issues. As for a fix? Find a way to keep water from collecting around the ECU connector.I just read your last post.... Checking ODB2 for codes won't produce any results. This issue is not a fault from anything that can be diagnosed by the OBD2, it's an "Act of God", so to speak, much like a mechanical issue that shows no codes. The issue is due to either 1... A lack of continual communication between your ECU (engine module) or TCM (transmission module) and any one of several other control units throughout your car, specifically the dash clusters (I was told it's the heater control unit, but I don't see why), OR, it's 2.... A result of rain water shorting out your ECU or TCM. I would first check for water on both front carpets, and your passenger side firewall, where your ECU harness plugs in to the ECU. Mine was totally submerged last big rain we had, so now I have had my windshield (windscreen) covered with plastic that goes under my hood a few feet so that rain water drains over the front of my engine while my car sits awaiting a warm enough day for me to diagnose a misfire at Cyl 3 (yay, remove the plenum) and pray it's a coil/plug and not a worn camshaft lobe. I've heard horror stories of worn camshafts in these engines.
Anyway, if you expect a bad rain, cover the windshield and tuck the ends into the doors and under the hood so that water can't run down the firewall. If you keep that ECU dry, I bet your Gearbox Fault disappears.

 

When I had the dreaded Gearbox Fault in 2016 I replaced the TCM (Tranny Control Module) in the left footwell. I bought a used one on Ebay for $40, waterproofed it per the video, swapped it out, and cleared the codes. Good for a couple more years.
Took about 5 minutes to swap out the TCM - four nuts and one plug.
Examined old one after removing - but did not seem wet or damaged in any way.

 

Meatbag, I will consider doing likewise if my fault returns again. I have heard a bad battery can cause this fault and I had been driving around with a had battery for a couple years, even going so far as to disconnect the terminals every night last winter until it warmed up in Spring. Then this winter, after 2 nights at 32°F, it died again, and a jump didn't get it working and after running with a misfire I decided it was time to replace it. After replacing I still had a misfire, and I then replaced the 3 plugs on the firewall side and the bad coil. Now it runs 100%, and I will see if the Gearbox fault ever reappears. But I am hoping that what I've read is true.... A bad battery in these cars can cause all sorts of problems.