the codes have been cleared a few times if that what ure talking about
Resetting or rebooting the ECU would be by removing power to it or removing a battery cable. Then waiting about 15 to 30 minutes. And then reconnecting power. That is like rebooting a personal computer. You power it off, then re-start it.
And you need to wait for awhile after disconnecting power because these have "capacitors
" which continue to supply power to the ECU after power is removed. It takes a bit of time for those capacitors to drain.
Removing power from the ECU on many vehicles
makes it lose its memory. I don't know if new vehicle ECU's have "non-volatile
" memory and would not lose their memory when power is removed?
Then clearing the codes would be with the unit powered up. You are telling the unit to delete the codes from memory.
Is the check engine light coming right back on when you start the car?
Or does it wait awhile, then come back on?