4low flashing engine light on after replacing both cylinder head gaskets

Hi,

Make sure no engine immobiliser DTCs are present and if the security is set. If present, It will have to go to Toyota dealer. Recheck all the connections and ground wires that was removed and make sure their in place and tight. I'm attaching repair guides and wiring diagrams for to reference and here are some preliminary checks to do first.
Review available vehicle history.
Review wiring diagrams and connector views for your specific vehicle application.
Check any fuses applicable to the circuit you are working on.
Follow all manufacturer warnings and cautions.
Check to confirm there are no aftermarket alarm or remote start systems.

https://www.2carpros.com/articles/how-to-reset-a-security-system

https://www.2carpros.com/articles/how-to-check-wiring