Hi and thanks for using 2CarPros.
The two codes are really separate from each other. One deals with an ignition issue and the other a coolant temperature sensor, either of which can cause a rough idle.
What I have done is attach the diagnostic flow charts for both conditions. However, I had to attach them in picture form. Read through them and see if they help. If there is something you can't read on them, let me know.
The ECU did not detect the ignition primary signal during starting or running.
Code 21 Ignition Signal Diagnostic Chart / See Pictures 1-4
The ECU detected an open or shorted circuit. (An abnormally high or low output voltage is entered.)
Code 13 Engine Temperature Sensor Diagnostic Chart / See Pictures 5 - 8
Let me know if this helps or if you have other questions.
Images (Click to enlarge)
Saturday, February 2nd, 2019 AT 10:43 PM