Originally Posted by hummerz

Fyi, Fuel Tank Pressure Sensors are one component of the vehicle's evaporative emissions control system. The sensor measures pressure changes within the fuel tank.

Originally Posted by Trog

I appreciate this information. Its a nice GeeWiz. I'm not sure why it's being brought up, because this issue is particularly with the Fuel RAIL Pressure sensor. All codes and issues were solved by this. the fuel RAIL pressure sensor is to measure that appropriate pressure for the Air/Fuel mixture is reaching the injectors located on the fuel rail. the tank is so far behind in the system it has its own pressure sensor, and that specifically reads that pressure to ensure the pressure valve is working and there is not too much back pressure.

Originally Posted by hummerz

Again, it's NOT a "fuel pressure sensor".
You fixed the P0451 Evaporative Emission System Pressure System
Which, had nothing to do with fuel pressure.

Originally Posted by Trog

Oh, Im sorry. I guess I am misinformed by the part I ordered to replace the faulty one. Ill send it back then. It is clearly a "pressure sensor". It was the problem. But please, continue to tell me how I am in the wrong.

Originally Posted by Trog

Daniel, thanks for asking again. I solved the problem. It was NOT entirely the fuel pump. It may have helped to change it, but there is actually a fuel pressure sensor hidden on the H3 Alpha. I'm not sure about other 2009s, but there is a fuel pressure sensor that the computer believes to be on the fuel rail. It is not on the fuel rail. On the 2009 h3 alpha, it is located between the cat converter and the transmission. if you are looking at the transmission from the front(engine side) it would be located about 3o'clock.

I found this by chasing the fuel lines. The lines come out of the pump(4 lines) and only 2 are easy to follow. The injection lines turn on the frame and go up the transmission, up into the engine bay where they are practically out of sight before connecting to the fuel rail. The pressure sensor is located on this line, youll have to chase it where it turns and follows the trans.

If your code is reading "Fuel rail pressure sensor A" like mine, it means it is not giving the proper reading, or a reading at all, and the hummer sputters a little because it is not sure what mixture to pump to the injectors. Eventually, it enters "limp" mode to keep it from stalling. These leads to foul smelling exhaust, poor gas mileage, and poor throttle response. I took the truck to a mechanic who hooked his Tech 2 scanner to the OBD, and it showed the reading from the sensor as "0" for fuel pressure.

Replace the faulty sensor by removing the little heat shield that "protects" the sensor from the exhaust heat. Then you'll need to grab a crows foot that fits over the sensor to attach to a ratchet. A regular open end wrench will not work because you cannot turn the wrench far enough to break the sensor lose. You'll need to give it one spin or so to be able to remove the plastic lock on the connector so you can disconnect the connector before totally removing the sensor. Then put the new one on, I found mine on RockAuto for 17 bucks. Now she runs beautifully.

Originally Posted by hummerz

Code P0446 indicates that there is an improper voltage drop in the EVAP Vent Valve circuit, which can be caused by either too little or too much electrical resistance. This improper electrical condition will cause the vent valve to malfunction.