Malibu V6-3.1L VIN J (2002)
Manifold Pressure/Vacuum Sensor: Testing and Inspection
Manifold Absolute Pressure (MAP) Sensor Diagnosis
CIRCUIT DESCRIPTION
The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold which gives an indication of the engine load. The
MAP sensor has the following circuits:
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A 5-volt reference circuit
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A low reference circuit
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A signal circuit
The powertrain control module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit and provides a ground on the low reference
circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to the pressure changes in the manifold. With low MAP
such as during idle or deceleration, the PCM should detect a low signal voltage. With high MAP such as ignition ON, with the engine OFF or wide
open throttle (WOT), the PCM should detect a high signal voltage. Certain vehicle models will also use the MAP sensor in order to calculate the
barometric pressure (BARO) when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the
engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range. If the PCM detects a MAP sensor
signal voltage that is excessively high, DTC P0108 will set. IF the PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 will
set.
DIAGNOSTIC AIDS
Inspect for the following conditions:
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Restrictions in the MAP sensor vacuum source
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MAP sensor seal missing or damaged
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Vacuum hoses disconnected, damaged, or incorrectly routed
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Intake manifold vacuum leaks
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Vacuum leaks at the throttle body
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Vacuum leaks at the exhaust gas recirculation (EGR) valve flange and pipes
TEST DESCRIPTION
