I figured it out. If you are interested in bringing up the engineering test mode for your car, I have found atleast one way to do it. It isn't exact yet as I only did it once and wasn't particularly paying good attention when I did it. But what you have to do is:

-Get into the car and leave your foot off the brake
-Depress the TRIP button on the end of the turn signal stalk and hold it in
-(with your foot off of the brake) Momentarily press the START/STOP button
-after 2-3 seconds of releasing the START/STOP button, release the TRIP button
-You should see the right portion of the instrument cluster tell you "Press Trip button to enter Engineering Test Mode".
-Press the TRIP button and see what happens.

For every press of the TRIP button, it will move on to another set of information. After about 10 pushes, you will get to the illumination screen where you can see everything light up on the instrument cluster. I don't know what everything means as I haven't had a lot of time to play with it yet. I am hoping that someone that may have attended some Jaguar Training or has the inside scoop on Jaguar information may have a list of what all the different indications may mean and how to decifer them. I know I have something for the X-Type that tells you all that information. I am sure there is something out there. But, it may also mean that i have some reading to do by going through the 3,000 page service manual to see if I can find the crumbs of info hidden here and there inside the manual.

I will be doing some more playing to see if I can get it to work with the engine running as I know some of the values should be used with the vehicle in motion (ie, speedo information, etc)

 

We have it on (some) S-Types, too.

Beware that the codes never get cleared e.g. mine are at least 7 years out of date as they were there when I got the car and still are. Best ignore them.

Some have found the raw fuel data useful for helping diagnose faulty level sensors. Not much else seems much use in actuality, but kinda interesting.

I suppose the voltmeter is vaguely useful but I own a meter...

 

I have been doing more playing and I can get the car to go into ENgineering Test Mode about 50% of the time using the above procedure. I am not sure what I am doing differently on the times that it is not working. So, if you try and do this, you may need to attempt it a few times.

Every time I get into my car, I am attempting to put it into engineering test mode just to do some playing and see if I can narrow down the specifics so it works 100% of the time.

More to follow.

 

Ok, I think I have it figured out. Now I need some other people to play with their cars to see if this holds true. Do not worry, there is nothing that you are going to do that can damage your vehicle. This is an information only mode that the instrument cluster goes into. There is nothing that you can change that will make the car do something detrimental.

The procedure:

1) Enter the car and leave your foot off of the brake
2) Depress the TRIP button and hold it for a minimum of 3 seconds before doing anything else
3) With the TRIP button still depressed, momentarily depress the START/STOP button
4) With the TRIP button still depressed, let the car start up the electronics until you reach the screen in the right most part of the cluster that says "Press the OK button" at the top
5) Release the TRIP button, you should now see the right most part of the cluster change to say "Press TRIP button to enter Engineering Test Mode"
6) Press the TRIP button one more time to enter Engineering Test Mode

Once in the ETM, you press the TRIP button to scroll forward through the various screens. Most of it is jiberish at the moment. where I do see it being helpful is near the end of all the screens, it does give a status of all the computers in the car. So, if you have a problem where you are stuck between having a sensor that is bad or a computer that is bad, this may be helpful in distinguishing between the two.

To exit this mode, simply turn off the car.

Can some other people attempt the procedure to make sure that what I am doing is correct. My times are based on counting to myself "one one thousand, two one th......."

If someone doesn't mind being a gineau pig, you can try doing this procedure with your foot on the brake to allow the car to start. From my experience with other cars, this should allow the engine to start but also put the instrument cluster into ETM mode. This will then allow you to compare signals of the speedo, tach, and possibly a few other sensors (don't recall what all was available) when trying to figure out if you have a bad fuel sender or if the problem is internal to the computer/cluster.

 

Does it have a tacho that closely matches the cluster tacho, and a speed (VSS) that is correct unlike the cluster (if the cluster overreads as I expect)?

 

JagV8, I know the tach has 3 different points that it shows you what the tach signal is. Whether these are limited in any fashion, I have not come across this information. I am just scratching the surface right now. As I find more information (got 3500 pages of a service manual to scour through), I will try and create a more indepth explanation of what you can learn from the car.

As for the speedo being correct, there is some amount of adjustment that the dealership can do. Keep in mind that the VSS in the car works by counting the number of pulses coming from each wheel's speed sensor and then converting that number to a relative speed. That conversion number is adjustable. So, if you know by what percent the speedo is off, the dealership (or a person with a dealership level computer) can go in and correct for this. There are limitations with this, but for our cars, without serious modifications, you should not hit that limit. But, this is as I understand how the signals are generated in the vehicle's electronics.

 

It's not quite that... if you use OBD you get the right speed. The cluster appears to be deliberately reporting a consistent higher one

 

JagV8, that is odd. The systems should all be grabbing the numbers from a common point. So, all points should be saying the same thing. If the cluster is reporting something different, then I would think that it has a problem. The only other "problem" that I could see is if there were modifications done and the cluster and the ECU (or ABS module) each pull the raw data from the wheel speed sensors. If the ECU was corrected to account for the modifications but the instrument cluster was not, then you would get an error that way. But, from my understanding, the ABS module gets all the wheel speed signals and that then averages and converts the signals to a speed. This speed signal is then sent out to the rest of the car to be used as needed.

 

I believe it's deliberate - to make sure they comply with the law (basically, not to under-read, so they over-read).

BTW it's not just jags that do this.