With Speed Density

A "Scan" displays manifold pressure in volts. Low pressure (high vacuum) reads a low voltage while a high pressure (low vacuum) reads a high voltage A failure in the Manifold Absolute Pressure (MAP) sensor circuit should set a Code 33 or 34 and using the chart will find the cause of the problem. A Code 33 may be set if a rough or unstable idle exists. CHART C-1D can also be used to check MAP sensor. Chart C-1D Manifold Absolute Pressure (MAP) Output Check