Chevrolet · GMC · Buick · Cadillac
GM OBD-II
DRIVE CYCLE GUIDE
A practical GM readiness guide covering common gasoline driving conditions, EVAP and catalyst requirements, and diesel aftertreatment cautions.
Drive cycle at a glance
Cold soak
When the monitor requires it
Warm and idle
Smooth operation
Cruise
Near 55 mph
Closed-throttle coast
Only when traffic allows
Cruise again
Maintain steady speed
Recheck
Identify the incomplete monitor
GM READINESS IS MONITOR-SPECIFIC
Chevrolet, GMC, Buick, and Cadillac vehicles use different enabling conditions across model years and engines. GM service information may call the exact procedure an Inspection/Maintenance Complete System Set Procedure or provide a separate procedure for the incomplete monitor.
A common gasoline starting pattern
- Begin after a cold soak when required. Keep the fuel level in the middle range for EVAP testing.
- Start without pressing the accelerator and allow the engine to idle while it warms normally.
- Use smooth, moderate acceleration to highway speed.
- Hold a steady cruise near 55 mph for several minutes.
- When safe, use a closed-throttle coast-down without braking.
- Return smoothly to highway speed and complete another steady cruise.
- Follow with ordinary city driving, complete stops, and idle periods.
- Recheck the individual monitor without clearing codes.
This is a practical starting pattern, not a universal GM specification. Exact speeds, times, temperatures, and accessory settings vary.
EVAP and catalyst considerations
GM EVAP strategies can depend on fuel level, ambient temperature, cold-soak time, barometric pressure, and key-off time. Catalyst and oxygen-sensor monitors generally need the engine fully warm, stable fuel control, and a steady cruise with no related pending faults.
GM diesel vehicles
Duramax and other GM diesel procedures may involve DPF, SCR/NOx, exhaust-gas-sensor, boost, EGR, and regeneration history. Some current GM service bulletins require multiple eight-hour soak periods and scan-tool-guided procedures after codes are cleared. Do not attempt a forced or stationary regeneration without proper equipment, training, and a safe approved location.
When to stop driving and diagnose
If the same monitor remains incomplete after several correct trips, check pending codes and service data. A monitor cannot complete when a required sensor, thermostat, fuel-control condition, or aftertreatment component is not operating correctly.
STILL NOT READY?
Bring the year, make, model, engine, fuel type, and a list of the incomplete monitors. The Smog Dawg can help you understand what the vehicle is reporting and what should happen next.