Why does the 4L light flashing on and off?

Known issue due to soy based insulation on wiring harness rodents chew on them harness will have to be replaced temp fix is remove ground from battery wait a few minutes resets computer

Where do they typically chew on the harness? Want to know where to start looking.

was this solved? curious, I am having the same problem

I had the same issue after towing using a 7 blade connector. Check the backup fuse in the dash panel fuse block. Might be blown. If not, its likely that it needs a repair harness installed from Toyota. Its a well known TSB(technical service bulletin)

Do you have a copy of the TSB?

I just looked up the tsb buuuut it applies only to 07 model years with a floor shift. Ill look again Monday for your model year