Riding along today on the road the trans light just popped on....
I drove to an exit shut the car off. Waited and started it up it was gone.
Then after about a half mile from when I started it came back on.
I thought crap maybe low fludid since I have a small leak.
I stuck a bottle in there.
Drove off and it still comes on.
It seems to get through all the gears fine. I have no idea what's up.
Is there anyway to pull the codes on this or does it require the old JDS which im sure nobody has anywhere these days?

 

I would love to hear of a fix for this symptom.

Redd will accelerate thru the gears,and go into lockup at 80 kms or so,no problem.When you put your foot down to cause a downshift to pass,POOF! and the lame light comes on.

Shut it off,restart,and no light,unless you want to do same again.

I can downshift manually,and sport mode causes crisper shifts,but it will not downshift on it's own.Maddening!

The Champ car works perfectly,goes like a scalded cat!

When I mucked out the throttle body on both cars,cleaned out the TPS,and reaffirmed the voltage/setting adjustment,Champ gave up an improvement!

I had to put Redd away for winter,so have not tested it out yet,but it's coming!

I do wonder if there is a kickdown solenoid in the tranny going west,and if there is,where is it?

Hopefully someone with some more insight will chime in...

Cheers,Jim.

 

Hi smgdata,

I assume you've checked the level and condition of your transmission fluid and it's right at the HOT line when the car has been driven at speed for at least 15 or 20 minutes, and the color is bright red and translucent.

I can't remember the year of your car (always a good idea to add the year, model and engine info to your signature line), but on our '93, the most common cause of the transmission warning lamp (and Limp Home Mode) has been oil contamination of the electrical connector for the Throttle Position Sensor (TPS). The TPS is mounted on the underside of the Throttle Body (TB), and on our car its electrical connector is mounted on a bracket on one of the intake manifold elbows just to the left of the TB. Spray out the connector with zero-residue electrical contact cleaner, allow to dry and reconnect.

If that doesn't resolve the issue, you may have oil contamination of the TPS itself. Because of where it is positioned, oil that is drawn into the intake through the crankcase breather system tends to drip down the butterfly valve shaft into the TPS, where it collects and eventually causes problems. Many owners have drilled drain holes in the TPS case so it can be flushed with contact cleaner. The holes are then left open so future oil contamination can drain out. Below is a link to photos showing how I did it on our '93:

Welcome to Jag-lovers - Members Photo Viewing Page


Another possibility is oil contamination or looseness of the main electrical connector on the left side of the transmission:

Welcome to Jag-lovers - Members Photo Viewing Page


If cleaning the TPS doesn't resolve the issue, follow John Ping's excellent diagnostic procedure and you'll track down the cause (you will need to register and log on to the Jag-Lovers forum, but it's free and there is lots of great XJ40 info there):

Jag-lovers' Ebooks


The only time our transmission warning lamp was not due to an issue with the TPS, I used John's procedure to trace the problem to the Transmission Control Module (TCM), where I found a cold solder joint:

Welcome to Jag-lovers - Members Photo Viewing Page


And a couple of other transmission-related services I've performed:

Welcome to Jag-lovers - Members Photo Viewing Page
Welcome to Jag-lovers - Members Photo Viewing Page


Cheers,

Don

 

Thanks Don I have a question for you I had a chance to glance over your reply im driving haha and I'm wondering if all of these will still work for the xj12 since it has the GM trans in it?

 

Hi Shawn,

I gather that your signature doesn't come through when you post from your phone.... I wish I'd known your car was an XJ81 before I did all that typing!

I'm not familiar with the GM 4L80E transmission, and I doubt that anything I said earlier will apply except regarding the transmission fluid level and condition, and oil contamination of the TPS or its electrical connector.

These cars are OBDI and an OBDII scanner can't interface with them, but you can read any stored Diagnostic Trouble Codes (DTCs) by using the Vehicle Condition Monitor (VCM). Turn the key to Position II (ignition on) without starting the engine. Depress the VCM button on the trip computer to the right of the steering wheel. Look in the small display window below the speedometer & tachometer for a message such as FF and a number, or Fuel Fail and a number.

Only one DTC can be read at a time, but there is a method for reading multiple codes by pulling a fuse in the center fuse box that works on the '93/'94 6-cylinder cars and just might work on your V12, so let us know if you find a code and I'll type up that method for you.

Cheers,

Don

 

As usual Don,you da man!

now that i have some more learning to do,I can't wait to shift the cars around,so I can drive MY Jag,instead of Cin's.

Finally get to see if there is any improvement over last year...
and pull the back glass...
and fix the AC.....

Cheers again..Jim.

 

I think the only way I'm going to figure this out. is to read the trans codes.
I drove around all day today. thought I was in the clear. then out of the blue it pops on.
seems to happen if I step on it. it's kinda random.
I'm pretty annoyed.
I wish the codes showed up on the VCM
who's has an old jds that works!!

 

@ SMGDATA

First I want to say this is my first post on this site. I've been on Jag Lovers for years, but there is lots of useful information here as well.

Always glad to see another '94 XJ12 owner. There aren't many of us. As for your transmission issue, I would bet you tank of premium that the issue is one or more shift solenoids. They are fairly inexpensive and not that hard to change. Yes they are inside the transmission and you need to drop the pan, but other than that it isn't very difficult.

Our v12's have so much torque its hard to tell when your missing gears unlike other cars. I was missing 1st and 4th with my bad solenoid. To test your transmission simply start from a dead stop and count the shifts. You should feel 3. The crazy part is these cars can still leave rubber starting out in 2nd gear! This is a very common problem and people freak out and sell their cars when all they need is a part that most auto part stores have for under $50. It won't be in their catalog so you need to know the part number. Same as any heavy duty GM truck with a 4L80E.

 

Hi TexXJ12,

Welcome to the Jaguar Forums! Thanks for contributing, it's great to have you with us. I've also been a member of Jag-Lovers for many years and agree that there is a wealth of knowledge there as well as many knowledgeable members.

Since we're a friendly group, please visit the New Member Area - Intro a MUST - Jaguar Forums - Jaguar Enthusiasts Forum and post an introduction so we can give you a proper welcome and learn something about you and your XJ12.

Enjoy the forum!

Cheers,

Don

 

I also have been a jag-lovers member since 2005. so much over there .


@TexXJ12 Hello fellow xj12 owner!!
Man i love getting on the freeway and punching it in sport mode. it just takes off, and that sound though alittle muted is pretty enjoyable to hear.
would be great to hear of any mods you have done, xjr shocks roll bars etc..
iv been looking around at things to update.
as for the trans it seems to be alittle random i have not driven it all this week.
As i remember i counted the gears as that was my 1st thought. i will need to do it again.
Now from what i remember it shifts perfect. then i notice the light on.
Seems to do it if i drive alittle hard. but as soon as i shut the car off wait 15 sec or so. turn it on no light.

 

When my transmission was acting up, it was most noticeable at highway speeds and not having 4th gear. When the transmission switch is in the "N" position it starts out in 2nd anyway, but I couldn't tell any difference with the "S" sport setting. Those were my main clues something wasn't quite right and the light would occasionally come on.

As I recall, changing the solenoid was only 1 or 2 small torx screws beyond doing a transmission filter. I read up a bunch on it before I jumped in and I think there are 2 solenoids, one controlling 1st and 4th and the other controlling 2nd and 3rd. The transmissions themselves are very tough. Basically they are a modern version of a turbo 400 and share some of the same parts.

My car is mostly stock, but I did put in an electric fan last Fall and it makes a big difference. I can really tell the engine has more power, revs quicker, run cooler, much much quieter, fixed my issue with the old fan rubbing on the shroud, and the best part is it helped with the mpg. I can get almost 17 on the highway now and between 13 and 14 in town. I will be watching the engine temperatures like a hawk though as the summer approaches (the real test). If you want some pics of it, let me know.

 

thanks for the info TexXJ12, would love some pics.
Well after a week and half i took her out tonight, drives good.
Im thinking once everything heats up, i have issues. Driving around and the dang light comes on. idk what else to do. i need a Jaguar PDU unit!!!

 

I'm thinking it might be TPS issues.
I took it out of the car and popped it opened cleaned the little sliders.
anyone know what the starting voltage should be?
I know on the old xjs ones it .32 v.

 

well thanks to everyone's info, it seemed to have been the TPS,
I had a used one sent to me that was on an XJ6, just stuck it on there and BOOM no CEL no Trans light, shes flying down the road again.


Don!! where do I send the Beer to?

 

Shawn,

Glad it was that simple.

Pick a good charity and make a small donation!

Cheers,

Don