So how do you pass emissions? IE - O2 ready status.
There are two ways to handle issues like this.
First, keep in mind that ECMs are used in multiple cars, so the sensor inputs are designed to be flexible. If the ECM is used in a 4 cyl, only two O2 inputs are needed. If the ECM is used in a V6, it has to be able to handle four O2 inputs. So the ability to either turn off a sensor input all together, or have an error ignored is needed in the ECM. The default state of the ECM is to assume that everything is working fine. The ECM does not look for affirmative answers that everything is good; it looks for things not working correctly. When it runs a test and observes an error, or when a sensor value is outside a normal range, the ECM has 3 primary options: Report an error immediately (i.e. the SES lamp is turned on), keep track of the error and see if it goes away (known as a pending error); do not report the error. Telling the ECM not to report the error means no problem is shown. So if the error code for the post cat O2 sensor were set to report no error,
when the car is scanned then no problems will be stored in ECM. The plug in emission testings looks for problems stored in the ECM. If the ECM says there are none, the car passes the test
Second, some tests can't be run until the car is warm or environmental factors (e.g., IAT > 0*f) are present. In that case, changing a criteria (e.g. run test when coolant is 160*) to a value that will not occur (e.g., coolant = 320*) prevents the test from being run and a negative result (i.e. error) is never generated.