Lights on in my 300. Code is po452. Evap pressure sensor? Ideas? Something plugged? Where us it at?

Check your gas cap.

I doubt it the gas cap because when the code says sensor in it it is usually and electrical problem most of the time but not always. If it was a leak from the cap it should have a code like "Evap Leak" since it would not hold pressue or vacum depending on what year it is. When the code says "Evap Sensor" it normally is not seeing a change in the sensor reading or not seeing and current flow thru
the sensor circuit. The controller will do a test first to make sure the sensor works as it will pump up the LDP or pull a vacum looking for the switch to show a change and verify it works. Once that passes it will do a leak test which is normally if it fails set a code like Evap system leak. If you tell us what year it is we may be able to look the code up for that year and give you the normal reasons for that exact code. It could still be a leak as there are times the PCM even gets fooled. Ron

it is a 2004 300m. Thanks. I at 1st thought yeah gas cap. Wife took it in to advance auto and had them do the reading and called me to tell me what they said.

thanks

corey

Bump for Ron

could be the small vacuum lines from the tank to the purge valve for the evap system.

OK that year should use the Natural Vacum Leak Detedtion switch system. I dont have the diagnostic book for it as they are nice and help alot to a specific code. From what I remember what happens is 2 things. When you shut the car down after driving the fuel will cool down some and pull a small vacum in the tank and then the NVLD switch will close and that tells the PCM its working ok. Then when the car is running in the right parameters the purge solenoid opens and purges the gas tank for a few seconds and pulls a larger vacum on the gas tank to see if it will pull the NVLD switch closed and if it does it will turn off the purge solenoid and see how long the tank will hold the vacum before the switch opens. Thats how it detects how large of a vacum leak it could have by how long it holds the vacum.
Both of the test like all OBDII test have to meet certain parameters before they run. Since the PCM moniters the switch wire it will know if its state changes from high volts (open) to low volts (grounded) and from what I remember if the switch volts does not change on either it sets the switch code thinking something is wrong with the switch or electrical circuit. It can also be a very large vacum leak in the tank and hoses but it only takes a very small amount of vacum to close the switch so it would have to be a good size leak to fail the second test. With a scanner you can moniter the switch and pull the connector and ground it to test the wires and then comand the eng to purge and pull a vacum to test it. Of course look for any cracked hoses or vacum leaks as they might cause it but most of the time that code can be a wire or NVLD switch problem. It would be nice if you know someone who will scann it for you if you cant find any visable leaks. Ron

Thanks Ron I'll check into that.

Corey