Originally Posted by ah1f39
Yes, and in Fords it is called '"limp home mode". If a $20 o2 cheater is installed the ECU will never detect an issue or enter the loop.
And o2 cheater don't allow for proper fuel metering they keep it set at one trim.
If properly removed and tuned you can get more power, but if anyone thinks running a car with the check engine light on is healthy or a proper performance moding there wrong.