Conditions for Running the DTC

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

DTCs P0642, P0643 are not set.
The engine is running for more than 0.5 seconds.
The ignition voltage is between 11-18 volts.
The intake air temperature (IAT) is between 0-150.75°C (32-303.35°F).
The engine coolant temperature (ECT) is between 57-99.75°C (134.6-211.6°F).
The barometric pressure (BARO) is more than 72 kPa.
The power take off (PTO) is not engaged.
The desired EGR valve position is more than 3 percent.
This diagnostic runs continuously while the above conditions are met.