Conditions For Running DTC

WARNING: This page is about a different car, the 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

The engine is operating on alternative fuel.
No AF ECM ECT, O2S or Gas Mass Sensor (GMS) DTCs are set.
The engine speed is greater than 500 RPM.
The battery voltage is greater than 10 volts.
The fuel tank pressure sensor indicates the CNG fuel level is greater than one-quarter full.
The engine coolant temperature is 176-221°F (80-105°C).
The AF ECM is not operating in a Fuel Cut-Off Mode (DFCO), speed limiting, etc.