What a baro sensor does
A barometric pressure sensor reads the pressure of the air around the car, not the pressure in the intake. That number moves with the weather, and it drops as you drive up in elevation. Thinner air means less oxygen per breath, so less power and a different fuel requirement. With a baro reading available, the ECU can log it for comparing runs on different days and use it in tuning corrections such as barometric correction.
The sensor itself is usually just a MAP sensor mounted where it sees outside air rather than manifold vacuum and boost. A 1 bar GM MAP sensor suits the job well, since a baro sensor never has to read boost. It's a powered sensor with three wires: 5V supply, signal to the ECU, and signal ground.
Setting it up in NSP
Wiring
Assign the signal to any free AVI (analog input). Turn the Pull Up off. The sensor drives its own output voltage, and an added pull-up would only skew it.
Calibration
The calibration tells the ECU how voltage relates to pressure. For a sensor bought from Haltech, click Load from File and pick the matching calibration. For anything else, enter the maker's voltage and pressure pairs by hand. If you've built your own, Save to File keeps a copy for the next car.
Display
- Warning Minimum: below this pressure, baro number displays, gauges and bars go into their low warning state.
- Display Maximum: where the gauge and bar end their scale. It also caps the highest pressure you can use in baro-related settings and tables, so don't set it too tight.
Diagnostics
You can turn on high and low voltage DTCs for the sensor, each with its own severity. The severity links the fault to an engine protection level. A voltage stuck near either end usually means an unplugged sensor, a broken wire or a short, so these are worth enabling on any car that relies on baro correction.
Quick checks
With the key on and the engine off, baro and manifold pressure should read almost the same, since the manifold is sitting at atmospheric pressure. If they're far apart, one of the calibrations is wrong. A baro reading that moves with the throttle means the sensor is picking up intake pressure and needs relocating.
