Circuit Check - With VCM-A

The Manifold Absolute Pressure (MAP) sensor is a pressure transducer that measures the changes in the intake manifold pressure. The pressure changes as a result of engine load and speed changes. The MAP sensor converts this to a voltage output.

A closed throttle on engine coastdown would produce a relatively low MAP output voltage, while a wide-open throttle would produce a high MAP output voltage. This high output voltage is produced because the pressure inside the manifold is the same as outside the manifold, so you measure 100% of outside air pressure. Manifold Absolute Pressure (MAP) is the OPPOSITE of what you would measure on a vacuum gage.

When manifold pressure is high, vacuum is low. The MAP sensor is also used to measure barometric pressure under certain conditions, which allows the Vehicle Control Module (VCM-A) to automatically adjust for different altitudes.

The VCM-A sends a 5 volt reference signal to the MAP sensor. As the manifold pressure changes, the electrical resistance of the MAP sensor also changes. By monitoring the sensor output voltage the VCM-A knows the manifold pressure. A higher pressure, low vacuum (high voltage) requires more fuel, while a lower pressure, higher vacuum (low voltage) requires less fuel. The VCM-A uses the MAP sensor to control fuel delivery and ignition timing.

Diagnostic Trouble Codes DTC(s) P0106, P0107, P0108, P1106 and P1107 indicate a failure in the MAP sensor circuit. Also refer to "MAP Output Check Diagnosis" to check the MAP sensor if there is no DTC. Refer to C Charts. Under Computer and Controls/System Diagnosis/Procedures. Testing and Inspection