Put the car in "ON" with the key. Find the ECU in the passenger kick panel, find the ECU diagnose screw, follow the instructions on the ECU to turn the screw.
Once your red light is flashing count the flashing check engine light.
First digit- slow flashes
Second digit- fast consecutive flashes.
In between codes, there will be a pause. If you get different numbers you have multiple diagnosis codes.
Google the numbers you find along with KA24 (whatever engine you have) then google how to fix those problems.