* The specific OBD-II monitors being tested: Different monitors have different requirements. Some require highway driving, some city driving, varied speeds, and specific engine operating temperatures.
* Driving conditions: Stop-and-go traffic significantly prolongs the cycle compared to consistent highway driving.
* Ambient temperature: Cold weather can slow down the process.
While some general guidelines suggest a drive of 50-100 miles might be sufficient *under ideal conditions* to complete many monitor tests, it's entirely possible to drive much further and still not have all monitors complete their self-tests. The best way to know if your drive cycle is complete is to use an OBD-II scanner that shows the readiness monitors' status. These scanners will tell you which monitors are complete and which need more driving.