Conditions To Carry Out The Diagnostic

To carry out the diagnostic, the following conditions must be met:

1. There are no DTCs registered for: Vehicle speed signal, canister purge valve, EVAP canister shut-off valve and fuel tank pressure sensor.
2. Fuel trim must be active
3. Engine must be idling
4. Speed 0 mph
5. Vehicle below 8202 ft. (2500m) above sea level
6. Outside temperature must be above 17.6°F (8°C)
7. Engine coolant temperature must be above 17.6°F (-8°C) and below 248°F(120°C)
8. Pressure in fuel tank must be above -.145 psi
9. Concentration of fuel fumes in the EVAP canister must not be too high

The diagnostic starts 17 minutes after starting the engine at the earliest, when all conditions have been met. It takes approximately 30 seconds. If the diagnostic is interrupted for any reason, it will try to start again the next time all conditions are met. ECM performs a maximum of 4 diagnostic attempts during an operating cycle. If no fault is detected the diagnostic will not run again in the same operating cycle. If a fault is detected two further attempts are made to evaluate the fault.