Possible causes

– Faulty Fuel Tank Pressure Sensor
– Fuel Tank Pressure Sensor harness is open or shorted
– Fuel Tank Pressure Sensor circuit poor electrical connection

Tech notes

On most Pontiac vehicles the sensor is on top of the fuel tank.

When is the code detected?

An excessively high voltage from the sensor is sent to Engine Control Module (ECM).

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0453 PONTIAC Description

The fuel tank pressure sensor responds to changes in fuel tank pressure. Vacuum is consider negative pressure. The information supplied by the fuel tank pressure sensor to the Engine Control Module (ECM) is used in order to detect vacuum decay or an excessive vacuum during the EVAP diagnostic routine.
The fuel tank pressure sensor signal voltage to VCM varies from a minimum of about 0.1 volts with pressure in the fuel tnk to greater than 4.0 volts with high vacuum in fuel tank.

http://cardiytool.com/images/14665.png

PONTIAC Technical Service Bulletins for P0453 code