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 manifold absolute pressure (MAP) sensor measures the pressure inside the intake manifold. Pressure in the intake manifold is affected by turbocharger output, engine speed, accelerator pedal input, ambient air temperature, and barometric pressure (BARO). A diaphragm within the MAP pressure sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates these changes into electrical resistance. The engine control module (ECM) supplies a regulated 5 volts on the 5-volt reference circuit and a ground on a low reference circuit. The MAP sensor provides a signal voltage to the ECM, relative to intake manifold pressures, on the MAP sensor signal circuit. The ECM converts the signal voltage input to a pressure value. Under normal operation, the lowest pressure that can exist in the intake manifold is equal to the BARO. This occurs when the vehicle is operated at idle or when the ignition is ON while the engine is OFF. The highest manifold pressures occur when the turbocharger output is high. Manifold pressure can range from 58 kPa (8 psi) when pressures are low to more than 295 kPa (42.7 psi) when pressures are high, depending on the BARO. The MAP pressure sensor has a range of 43-365 kPa (6-53 psi). The ECM monitors the MAP sensor by comparing a calculated predicted value at a predetermined engine load and speed, to the actual sensor input.