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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G2500, VAN CARGO, 6.6 6REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1065 (ENGINE CONTROLS AND FUEL - 6.6L (LMM) - DTC P0016 TO DTC P0299)DTC P0101CIRCUIT/SYSTEM DESCRIPTION
2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6

Circuit/System Description

2008 Chevrolet Chevy Express G2500, Van Cargo, 6.6 6SECTION Circuit/System Description
WARNING: This page is about a different car, the 2007 GMC Sierra, 2007 GMC Cab & Chassis Sierra, 2007 Chevrolet Silverado, and 2007 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The mass air flow (MAF) sensor is integrated with the intake air temperature (IAT) sensor. The MAF sensor is an air flow meter that measures the amount of air entering the engine. The engine control module (ECM) uses the MAF sensor signal to provide the correct fuel delivery for all engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle condition. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF/IAT sensor has the following circuits:

  • A MAF sensor ignition 1 voltage circuit
  • A MAF sensor ground circuit
  • A MAF sensor signal circuit
  • An IAT sensor signal circuit
  • An IAT sensor low reference circuit

The ECM applies 5 volts to the MAF sensor on the MAF sensor signal circuit. The sensor uses the voltage to produce a frequency based on the inlet airflow through the sensor bore. The frequency varies in a range depending on engine coolant temperature (ECT) of approximately 2,300 Hertz at idle to near 9,000 Hertz at maximum engine load.

When engine coolant temperatures reach 60°C (140°F) the ECM commands a Rich Idle mode. During Rich Idle the exhaust gas recirculation (EGR) valve is commanded ON, and a lower frequency and g/s value will be indicated on the scan tool.

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