Question

1999 Toyota Yaris 1.0L with engine code P1315, which ignition coil is faulty?

Answer 1

#4, you count the cylinder numbers from left to right. 1, 2, 3, 4

check the spark plugs first if bad replace it and reset light, if the plugs are good and problem is still there swap the coils and see if the problem is still there, if so check injectors and so on. Also check for intake leaks

Answer 2

P1315 TOYOTA - Igniter Circuit Malfunction No. 4

Read more: https://www.autocodes.com/p1315_toyota.html