Chosen Solution
i got this check engine light everytime it rains . i scan the code and it show p700 . ( transmission failure ) however the car run okay no problem and after 2 days of doing running the check engine light will turn off.
It could be a number of issues but when you said it mainly happens when it rains then i would put money on it being a bad connection in the wiring harness to the transmission. Maybe water causing a short circuit & then once it’s dried out the transmission control unit thinks the fault has cleared. I would follow the wiring harness from the left side of the dash, through to the gearbox. Checking for any breaks in insulation & also the security of any connector blocks outside of the interior of the vehicle. I know the Subaru Forester has 2 BIG connector blocks on the top of the gearbox around the bell housing area. It maybe the problem lies in those. Google your transmission wiring harness & see what the photos show you. Good luck
