Barometric Pressure Sensor: Testing and Inspection

Fig. 008 - Chart C-1D Map and Baro Output Check:

NOTE: MAP and BARO sensors are essentially the same device--one--MAP--measures the difference between pressure in the manifold and atmospheric pressure, and the other--BARO--measures atmospheric pressure.

1. Check that sensor voltage is highest when manifold pressure is highest--output normally is in the middle range for specific altitudes.
- Low voltage increases spark advance.
- High voltage decreases spark advance.
2. Check to see if the rate of change of the output VS change in pressure is correct--normal change would be about the middle of the range listed.
- The voltage should change as soon as the vacuum is changed.
- If it doesn't, it could result in detonation or a sag on acceleration which could also be caused by fuel or a restriction in the hose to the sensor.