Diagnostic Aids
With ignition on and engine stopped, manifold pressure is equal to atmospheric pressure and the signal will be high. MAP sensor is also used for altitude compensation. This information is used by ECM as an indication of vehicle altitude and referred to as Barometric (BARO) pressure. Comparison of the voltage signal with the reading of another known good unit is a suitable way to test the accuracy of a "suspect" sensor. Voltage reading should be within 0.4 volt of the good unit. A Code 33 will result if circuit No. 450 is open, or if circuit No. 432 is shorted to voltage or shorted to circuit No. 416.