The Jag representative on the UK part of this forum invited us to submit any general questions, so I took the opportunity to clear up a few of the XK topics that have been discussed over recent months:

Q: Are the adaptions learned by the TCM lost (i.e. reset to factory settings) when the battery is disconnected?
A: No, the transmission settings are not lost when the battery is disconnected and can only be reset by the SDD diagnostic tool.

Q: Do the active exhaust valves on the 5.0 XKR/R-S open when Dynamic Mode is selected?
A: When the transmission is in the manual (sequential shift) mode, the exhaust valves are permanently open. When the transmission is in the normal or sport mode, the position of the exhaust valves depends on engine speed and load. [I take this to mean, "No"]

Q: Does the Adaptive Damping system change its settings immediately when Dynamic Mode is selected, or does it take up to 30 seconds like the ECM changes?
A: Adaptive damping settings change immediately

Q: Should permanent wiring for a battery maintainer on a 5.0 be connected direct to the battery terminals or should it be connected 'outside' the battery monitoring module (so that the charging current can be seen by the module)?
A: If you are using a normal charging lead, red lead goes on the positive post and black lead connects to a chassis ground point.

Q: In 'S' mode on a 5.0, does torque-converter lockup happen faster than in 'D'?
A: No changes; 'S' mode changes the transmission software maps only.

Q: In 'D' mode, does an XK/XKR normally select 2nd gear when accelerating moderately (i.e. not full throttle) from a standstill?
A: This can happen depending on how enthusiastic the driver is, This is to provide better torque and acceleration. [I read that as, "Sometimes". I don't quite see how starting in 2nd enhances anything except fuel mileage, but...]

Q: Does keeping the key fob within range of the sensors of a car with keyless entry cause increased battery drain?
A: No, as this feature requires the customer to open the door handle before the controller area networks are woken.

So there you have it, from the correct end of the horse

 

I TOLD YOU SO ....







<- SARCASM ....!!!

 

Just to make this clear: when the battery is disconnected, the engine control adaptations ARE lost: from the Technical Training Manual for the XK :"Engine control adaptations are lost when the battery is disconnected. On reconnection, some slightly abnormal drive symptoms may occur." No such comment is made about the transmission control adaptations

 

That's the ECM, not the TCM - I was asking specifically about the TCM, because it is not stated either way in the workshop manual. And there's a procedure to allow the ECM to start re-learning its adaptations, so that those symptoms are minimised.

 

Thank you for this. So I am clear, I can leave the key fob in the car? Thats by far my biggest issue!

 

Looks like I am going to have to change the black lead from the battery post to a ground.

 

Yes - however, you can't lock the car if you leave the fob inside:

And, if you don't lock the car, it takes longer to completely power down, and that drains the battery. Not a problem if you use a battery maintainer or drive it for a decent distance regularly.

This question related to a list of things that were proposed as necessary if you want to keep the battery level up. Locking the car was the main one, but there were claims that you should keep the key at least 3m from the car - that turns out to be incorrect. But the locking one is true.

 

That also happens to be a great way to get locked out of your car if you don't have the second key handy...

 

still a little unsure. Sorry, I am talking about keeping the key in the car only when parked in my garage. Its not stored, I drive it at least 3-4 times per week. Is that a problem?

 

As long as you drive it regularly, you should have no battery problems from leaving it unlocked, so: yes, leave the key in it.

But if you start to have weird electrical problems or dashboard warnings that appear and then go away when you re-start, your battery may be running low, and you should consider using a battery maintainer to keep it topped up. The XK sucks power at a phenomenal rate, and a low battery really messes with it.

 

Thank you so much.

 

No prob - you must live in a safe town! I always hide my keys, because it's become common practice here in the UK for burglars to steal your car on their way out if you leave the keys in the open. In addition, car thieves will break in so that they can get the keys & take the car undamaged - particularly when stealing high-value cars.

 

This thread makes me think my "P0687 ECM/PCM Power Relay Control Circuit High" is really a weak battery message.

 

Mine is a dd and I routinely leave the key in the car when it's in the garage. I've done this since I bought the car two years ago. The electrical gremlins went away after I installed an AGM battery 14 months ago. Based on my experience I don't see that leaving the key in the car causes any problems.

 

That would be P068773, "EMS control relay control circuit high". EMS is the Engine Management System, and that relay turns on pretty much everything - the ignition, injectors, fan, etc. It's controlled by the ECM, so the 'control circuit high' is referring to the link that connects to the ECM.

The way it appears to work is: the relay control is permanently connected to the battery on one side, and to the ECM on the other. When the ECM wants to turn the relay on, to 'power up' the rest of the engine's systems, it earths its side of the relay, allowing current to flow and causing the relay to close. So when the control signal is low, the relay is on and the engine electrics are powered up.

So what does "control circuit high" actually mean, and how is it being measured? I'm not sure. If it is being measured by the ECM, then I would expect that circuit to be high until the ECM pulls it low by earthing it. So what's wrong with it being high?

The "Possible Cause" listed in the workshop manual is "EMS control relay malfunction". So, maybe consider replacing that relay if the code keeps coming back. Do you actually have any trouble starting the car?

 

The burgulars aren't afraid of getting shot? Oh, wait...UK. Sorry...

 

Yeah - the good news is, I'm not worried about getting shot, either.

 

The exact code is "P0687 ECM/PCM Circuit High"

We replaced the control module last season and still get the issue, but not as much. After the XK's winter rest, the code came back twice. I really think it's the battery at this point. Still the original battery in an '07.

 

Your code reader can't show the full 7-digit Jaguar code, which is P068773 - anyway, it's the same thing.

Well, since the battery is 7 years old, it would probably be prudent to change it anyway. When they get older, they're less resilient, and they tend to collapse suddenly at the least convenient moment. If the problem persists, you may want to take a look at that relay, which I believe is R11B in the Power Distribution Box (the fusebox in the engine bay).

 

Great post, thanks!


Rich