Century V6-3100 3.1L VIN M SFI (1998)
Manifold Pressure/Vacuum Sensor: Testing and Inspection
MAP Sensor Service
Following is a short description of how the Manifold Absolute Pressure (MAP) sensor (5) can be diagnosed by using a scan tool. The scan tool can also
be used to compare the values for a normal running engine with the engine you are diagnosing.
DESCRIPTION
The Manifold Absolute Pressure (MAP) sensor (5) responds to changes in intake manifold pressure (vacuum). The MAP sensor signal voltage to the
PCM varies from below 2 volts at idle (high vacuum) to above 4 volts with the key on, engine not running or at wide open throttle (low vacuum).
OPERATION
The MAP sensor (5) is used to determine manifold pressure changes while the linear EGR flow test diagnostic is being run (refer to DTC P0401), to
determine engine vacuum level for other diagnostics and to determine barometric pressure (BARO).
DIAGNOSIS
If the PCM detects a voltage that is lower than the possible range of the MAP sensor, DTC P0107 will be set. A signal voltage higher than the possible
range of the sensor will set DTC P0108. An intermittent low or high voltage will set DTC P1107 or P1106 respectively. The PCM can also detect a
shifted MAP sensor. The PCM compares the MAP sensor signal to a calculated MAP based on throttle position and various engine load factors If the
PCM detects a MAP signal that varies excessively above or below the calculated value, DTC P0106 will set. Refer to System DIagnosis / Diagnostic
Tables / Diagnostic Trouble Code Tables. See: Testing and Inspection
The PCM updates the MAP sensor reading at each 3X reference pulse. If the 3X reference pulse is lost the PCM will only update the MAP sensor
once per ignition cycle and will retain that value until the next ignition cycle. Depending on the retained MAP sensor value the PCM will set the
appropriate high voltage DTC or low voltage DTC.
