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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 31 (ENGINE CONTROLS - THEORY & OPERATION - 8.1L)FUEL SYSTEMSFUEL CONTROLCLOSED LOOP MODE
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Closed Loop Mode

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Closed Loop Mode
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When HO2S reaches operating temperature, coolant temperature reaches a preset temperature and a specific period of time has passed since engine start-up, PCM operates in closed loop mode. In closed loop mode, PCM controls air/fuel ratio based upon HO2S signals (in addition to other input parameters) to maintain as close to a 14.7:1 air/fuel ratio as possible. If HO2S cools off (due to excessive idling) or a fault occurs in HO2S circuit, vehicle will re-enter open loop mode.

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