npappasan

So my 03 e55 was previously doing the dang red check gas cap warning with CEL. It was throwing out a p0455 large EVAP leak code. Got a new gas cap with no luck. Changed the purge valve solenoid under the hood with no luck. Then worked my way back to the charcoal canister. I could intermittently smell gas at the right rear wheelwell. The canister looked intact. Took out the canister vent solenoid and the O ring was pretty shot. I replaced with new canister solenoid and O ring and that seemed to work. No warning or CEL for almost a month!

Until today....

Red gas cap warning and CEL came on today. Now the code is a p0451, which seems to indicate a faulty fuel pressure sensor.

Can’t seem to get any straight info on this sensor online. Where is it???? Please somebody help!

npappasan

Bump

bbirdwell

Fuel pressure sensor is located on top of the fuel filter under the driver's side rear seat. It's part of the fuel filter assembly so hope it's just a bad connection and not a bad sensor.

npappasan

Thanks. But it looks like the sensor can be bought as a stand alone separate part. I was getting the same vibe as what you’re saying but why would it be sold as part that looks like it would unclip from the bracket it is in?

npappasan

npappasan

It looks like a plain old sensor. Mounting clips. Electrical connector. Etc.

i guess I’ll just have to remove seat and look at it.

npappasan

Doesnt make sense that it would be available as a part if it were a fixed component of another part.

bbirdwell

Go for it and let us know. Would be a good DIY.

npappasan

Well, I’ll look at it first and see how the sensor is connected/attached and go from there. Not really any solid info on this out there.

Ivan-2019

Any update on this one? Getting the exact same problem on my 2004 E500. Replaced the charcoal canister, shut off switch, purge valve, gas cap and getting the red fuel cap warning after about 30 to 60 minutes of driving.

npappasan

Cleared code after I originally posted this and light hasn’t come on since.

npappasan

Check under hood at back of driver side intake. That vacuum/EVAP hose is notorious for wiggling off.

Thats what mine turned out to be after replacing everything also like you have.