Driving cycles and warm-up procedures are required to complete GM evaporative emission system monitors.
To get the EVAP monitor ready on GM vehicles, complete a specific drive cycle that includes cold starts, steady-speed driving, and varied throttle inputs. This allows the onboard diagnostic system to test for fuel vapor leaks and purge system functionality.
GM EVAP Drive Cycle Overview
- Cold start engine when ambient temperature is between 40-90°F
- Idle for 2.5 minutes with A/C and rear defroster on
- Drive at 55 mph for 3 minutes
- Decelerate to 20 mph without braking for 2.5 minutes
- Accelerate to 55-60 mph and maintain for 5 minutes
- Decelerate to stop without braking for 2.5 minutes
Common GM EVAP Monitor Readiness Methods
| Method | Time Required | Difficulty |
|---|---|---|
| Standard Drive Cycle | 15-20 minutes | Moderate |
| Fuel Tank Level Adjustment | 5-10 minutes | Easy |
| Professional Scan Tool | 5 minutes | Easy with tool |
Tips for Successful EVAP Monitor Completion
- Fuel tank should be 1/4 to 3/4 full
- Ensure fuel cap is properly installed and sealed
- Disconnect battery for 15 minutes if monitors are stuck
- Address any stored trouble codes before attempting drive cycle
- Drive on flat terrain when possible for consistent results
Troubleshooting Incomplete EVAP Monitors
- Check for pending trouble codes
- Verify EVAP system components are functioning
- Ensure ambient temperature is within required range
- Confirm fuel level is appropriate
- Repeat drive cycle up to three times if necessary