Third brake light wiring

[JEMSRubicon]

I'm installing a SMI stay and play braking system on my JLU and need a brake light signal to operate the system. I'm using the CoolTech system for brake lights from the RV so the brake peddle switch will be disabled. It is my understanding the brake peddle switch also time out after 5 minutes. However I understand the brake light over the spare tire does not time out, so my question is does anyone know which wire (I'm assuming in the lume at the passanger door) powers the brake light over the spare tire and I can use this as the required brake signal. Or any other suggestions would be appreciated

Thx

Sponsored