GrendelKahn

Anyone know how to correct this problem? I get 2 OBD codes:
P0450 - Evap emissions control system pressure sensor malfunction
P0453 - Evap emissions fuel tank pressure sensor high input

I've changed the 3-way valve leading to the charcoal canister, the canister vent shut off valve, the pressure regulator from/to the intake manifold. I tested the purge control solenoid and it seems OK, but I could be mistaken.

I've reset the PCM each time, but after running for a bit the check engine light comes back on. I also have a lope in the idle once the engine warms up, but I've assumed this is related to the Evap problem, and not something separate. Haven't rechecked the ODB codes since before I started replacing things either though.

I'm at a loss for what to do now ...

chris_v2

You need to find out why the FTP is sending a high output. Most likely the actual FTP has failed, but I would check out it's data PID while I purge the system to make sure it's functioning properly.

arc_55

Agreed if you can access data through your scanner you will notice system pressure/vacuum. On a good scan tool you will be able to command the purge valve. If not you will have to manually do it by backprobing the connector.

You can also do a vacuum test with a vacuum pump. I think you have a fault in either the wiring or the sensor but you can monitor it through data in the scanner.

GrendelKahn

Thanks for the feedback.

Unfortunately I don't have the code reader anymore though. It was on loan, and was just a basic model anyway.

Hopefully it's just a bad hose that I can replace easily. Otherwise this is turning into a much bigger job than I had anticipated.

Any thoughts on the idle cycling up and down? I haven't found any bad vacuum lines or leaks, and I'm now thinking this is not related the emissions sensor issue if that is due to a bad fuel tank sensor.

chris_v2

The idling fluctuation is caused by the IACV. Try cleaning it before you replace the part.

arc_55

the ftp sensor is located on the tank so there is nothing inbetween.