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P0452 sets when the evap pressure sensor's signal drops too low and out of a normal signal range. The pressure sensor is mounted just forward of the trunk floor/spare tire area underneath. It receives a reference voltage and sensor ground and then creates a signal based on pressure in the evap system.
This code can be set by the sensor's wiring, the ECM (very unlikely), or the sensor itself. If the code resets immediately when cleared then the problem is current and can be diagnosed, but if it's an intermittent problem then electrical testing wouldn't help if the problem wasn't present while testing was being done.
At the time it's acting up you should find 5v on the purple wire in pin 3 (on right of connector, facing terminal end) and ground on the brown/orange wire. If these are ok then you can jump the two purple wires and it should then set a P0453. If it does then replace the sensor.
The airbag light is on because the airbag module has seen a problem somewhere in the system and set a fault code. The problem could be anything from a bad airbag module to the bags themselves, seatbelt pretensioners, clockspring in the steering column, impact sensors, wiring, etc. The first step in diagnosing the problem is using a capable scan tool to see what fault codes have set in the airbag module.