Dodge Ram 2003 with hemi

Barometric pressure comes from the map sensor at key on engine off and wide open throttle position bc there is no engine vacuum at that point... low means you probably have a shorted map sensor

Use a volt meter and back probe the signal wire with the key on and sensor unplugged, its a three wire sensor... 5 volt power wire, 5 volt signal wire and a ground... the signal wire should not be pulled to ground with just the key on while plugging the sensor in