Where is the lid sensor located in the MBP 15" mid 2012?

I just bought a second hand MBP 15 mid 2012 and everything seemed fine until I realised that it does not sleep when the lid is closed.

It has a clean install of Catalina, I’ve checked the system settings and I have tried all the usual steps, zapped the PRAM and reset the SMC.

It was suggested that it might be the SATA cable on the SSD but I’m not convinced. I have learned that the lid sensor on the 13” model is located within the battery indicator assembly and comparing the 13” and 15” battery indicator assemblies, apart from the shape of the ribbon cable, they look identical. However, the description of 13” ones often includes the words sleep sensor and I am yet to find a 15” one which does. That said, I have discovered that the battery indicator light does not work on my MBP, the button does not press and the LEDs consequently do not illuminate.

I have performed some hairy MBP surgery before, having replaced an LCD panel but I have never removed a logic board which would be required to replace the battery indicator so even though they are pretty cheap to buy, I’d rather know that this is the likely culprit before I scrub up.