The MAP sensor measures changes in manifold pressure. Changes in manifold pressure result from engine load and speed changes. The MAP sensor converts these changes in manifold pressure into a voltage output signal to PCM (about 1.5 volts at idle to about 4.5 volts at WOT). The PCM can monitor these signals and adjust air/fuel ratio and ignition timing under various operating conditions.
If MAP sensor fails, PCM will substitute a fixed MAP value and will use the TP sensor to control fuel delivery. Failure in MAP sensor circuit should set a related Diagnostic Trouble Code (DTC). If a related DTC is not present and MAP sensor is suspected of causing a driveability problem, perform a functional check of MAP sensor. See SYSTEM/COMPONENT TESTS article.