How do I get readiness monitors to complete after a repair?
Short answer: Drive the vehicle through the manufacturer's drive cycle, which usually includes a cold start, idle, steady cruise and deceleration, with a fuel level between about a quarter and three quarters.
Each monitor has enabling conditions. The EVAP monitor often wants a cold soak overnight, a fuel level within a set range, and a specific ambient temperature. The catalyst and oxygen sensor monitors usually need a fully warm engine and several minutes of steady cruise followed by deceleration without braking.
Start with the drive cycle procedure for that make and model, found in service information or in many scan tools under readiness or I/M. Generic drive cycles exist, but manufacturer-specific ones work better. Some scan tools also show which enabling conditions are not yet met.
A few manufacturers offer a scan tool routine that runs the EVAP test in the bay, which saves road time. Keep the trip safe and legal; do not try to hit drive cycle speeds on busy streets. If a monitor will not complete after several proper cycles, check for a pending code, a thermostat that keeps the engine from reaching temperature, or a fault that blocks testing.
Tools used for this job
General guidance only. Follow the vehicle and tool manufacturer's procedures, and confirm vehicle coverage on the tool maker's list before buying.