Just how long should it take, till P1000 pending code leaves? Light has been off for several drive cycles as well as over night's. Code is only visible on the scanner, but want to be able to pass E check with out the tailpipe test. Heard some areas will no longer pass your car, unless their plug in unit, ok's things.

 

P1000 is a pending code which means that not all of the supported OBD monitors have run OK. It won't itself cause a fail but the unset monitor(s) may (depends on region etc).

Any time you clear the codes you'll get P1000 as it also clears all the monitors, so if you're clearing the codes that is immediately why you have P1000.

Otherwise, your best bet is to read the status of each monitor, which many OBD tools will do, and also check for actual or (other) pending codes.

If happy, you'd get a pending P1111 and like P1000 it won't cause a fail as it's only a pending code.