So I misread your earlier post Puddlian and I actually believe I know what that cable is. I believe you are referencing the "Park Override" function, which is used to get the vehicle out of "Park" so it can be towed. If that's the case, in the owner's manual this is covered in section 5.5 and suggests that this override lever is under the driver side rear seat, where you're currently referencing. In the owner's manual it gives a diagram and a "how-to" for utilizing that cable and it may not be a bad idea to simply reset it to see if it helps your issue.

Per the manual:

"Apply the handbrake. Remove the LH rear seat base (A) and
unscew the two screws that secure the park override lever
cover. Remove the cover.
Pull the manual park override lever (B) fully up on the
ratchet, fully releasing the parking lock.
After towing or moving the vehicle apply the handbrake. Lift
the manual park override lever slightly, press the ratchet
release (C) and lower the manual park override lever back to
the stop. The parking lock is now engaged. Install the cover
and the rear seat base.

The message in the instrument pack must disappear and
the position display must change from ‘N’ to ‘P’.
Otherwise there is the danger that the vehicle will roll
away."

 

This is all super useful stuff...thanks. Last night I downloaded a workshop manual for the DB9 from a British site "Service Manuals Online" and spent most of this morning paging through 2472 pages of schematics and P codes, in an attempt to figure out how my DB9 puts itself in Park!
CCFULTON's diagrams from the ZF manual were something I hadn't seen yet, so that was awesome. But I still can't resolve in my head whether there are two separate systems that invoke the Park feature on the gearbox. What I unearthed under the back seat is obviously for disengaging the Park mode when you break-down and need to be towed.... So you pull the wire loop and it puts the car in Neutral. I get that.... but when I push the P button on the console, does that same cable activate the same pawl to engage a Park mode in the gearbox, or does the same pawl get engagedindependently by a "Shift-By-Wire" system? So when I crawl under the car, will I find another cable system and lever on the side of the transmission housing that can be adjusted (as shown in CCFULTON's diagram from a BMW)....?
When I looked at all the exploded diagrams in the workshop manual, I see no indication of a second cable system but I recall reading this on the Pistonheads Forum ..."I got there around 3.45pm and Matt was out to see me within a couple of mins along with one of his technicians. They had a play around with the buttons and eventually within minutes diagnosed it to be a wire that runs under the car (parking break wire or something :???: ) being too tight. After a slight adjustment it was all sorted and no more error messages on the dash! P also engages without problem now......." ....So I am hoping that I can mimic the euphoria that this individual experienced. Wish me luck. And thanks again to CCFulton, AstonCarma and HSM-Precision

 

I have not been under my car and looked at it myself to absolutely verify but I believe that ZF builds the transmissions with either a cable PRND selector or an emergency release but never both. If you think about it, it would be redundant to have both. If you have a physical cable that can put the transmission into N with a shift lever, then there is no need for an emergency release.

But if you ONLY have an electrical system to select gears, as is the case in the AM version, then you need a failsafe to get the car into neutral in the event there is an electrical fault. The buttons are electrical and connect to the TCM via both a direct connection from the Center Console Module and also from the ECU.

Assuming there is nothing wrong with the transmission itself, the problem will either be that the emergency cable is adjusted poorly and pulling on that release lever when it should not be and putting the transmission into some in between P and N state. Or it will be an electrical problem that the mechatronic is not getting a clear "Should be in Park", "Should be out of Park" signal.

All of the electrical connections to a 6HP come through that one round connector on the mechatronic. Every version of the 6HP I've ever heard of has a propensity to leak around that connector seal but in most cars it will leave a drip on the floor and you will know it's time to replace the seal. With that rear plate under the transmission, a DB9 could probably be leaking pretty badly and you would never know it.

That's why I suggested that you also take a close look at that connector and harness while you are checking the cable. If it's leaking and and the connector is full of trans oil, or just dirty or the wires are pulled in a funny way, you might get some flaky behavior.

If you do find signs of a leak you will also want to check the fluid level just to be sure.

 

Puddlian, I also recommend checking out https://www.6speedonline.com/forums/...k-failure.html from OldPhart. He's still active on these forums as of today but never updated his issue (which I wish owners would always do when they post a problem). Maybe PMing him might turn up something as well?

I offer this as I don't know the answers to your other questions, sorry. Forum members like Irish, J Double and some others may know those answers though. They seem to really understand the ins and outs of these vehicles well.