C2310 and P-lock malfunction

I have been reading through this forum several times to try and figure out how to troubleshoot my P-lock malfunction error. It started to warn me intermittently, to later on be a permanent error. However, the P-lock does engage (it wont roll), both on P button press, and ignition off, but the indicator LED on the button doesn't lit up. The P-mode in the dash will show the correct state though. The car drives and behaves normally, but occasionally (and more often recently), the battery will drain completely over night which might be related to the dashboard sometimes actually lit up with the warning, even though the car is off.

My "easy" remedies so far has been to replace the 12V battery, and replace the big white relay in the engine fuse box (I have access a second identical car that I can "borrow" parts from).

Now, none of these has helped, and I have gotten the error code stored from my shop (C2310), which says according to documentation I've found:

Open or Short Circuit in Battery Circuit

And possible causes

- P CON MAIN fuse (I've checked the fuse, of course, and the P-mode works)
- Transmission control ECU assembly
- Wire harness or connector

Now, the questions I have are:

How do I reach the P actuator thing? That is mounted onto the transmission (to check the connector and the wire harness)? I've figured out I have to reach it from below the car, but can someone give more details on what side and if it is facing front or rear of the transmission?

Anyone know where the Transmission control ECU assembly is located?

The shop is gonna charge me around $350 just for troubleshooting, so I just wanna see if there are some means of troubleshooting I can do myself first and foremost.

Any hints would be greatly appreciated!

 

I managed to find the Transmission control behind the glovebox, it was the black box in there with two white connectors. Following the wiring diagram I read the voltage on pin 15 on the A23 connector which should have a permanent 12V on it, and it reads 0V. No measurable resistance to GND, so it is at least not shorted.

Now, There is 12V on both end of the P CON main fuse, so seems that the wire somewhere in between has got damaged. There is supposedly a junction connector which is labeled A52 and A53 in the wiring diagram, however I haven't found any documentation on where the junction connectors reside, which makes it a bit hard to verify the voltage there. On the plus side, this should confirm that the Transmission Control is intact at least

Someone (probably the initial dealer) has installed an engine heater and zip-tied the heater cable onto the harness close to the center of the engine room, which if I'm unlucky has teared off the cable in there. The zip tie is proorly placed, just outside of the harder, plastic tube that hosts the harness, which means that the only thing between the cables and the zip tie is some black tape. However, it is really tight and impossible to visually inspect in place, I need to either make room by removing stuff, or it would be possible to get the harness out for inspection...

If I could just find the junction, I could at least identify which section of the harness that is damaged.

And just to repeat, I did change the 12V battery first thing when this started to occur. It was 7 years old so it was due replacement either way, and I've now verified that the BATT cable for the transmission control is indeed lacking power.

 

I think rodent damage is unlikely, I don't think that is very common here in Sweden, but I don't know. It has done around 110k kilometers, which is around 70k miles. It's the first year of gen3, 2010 and produced in 2009.