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I've been dealing with tracking down a persistent P0455 (evap large leak) code.
So far I have:
1) Replaced Gas Cap
2) Replaced Purge Valve under hood
3) replaced white cannister valve under rear bumper
4) Smoke tested system to find no leaks
The only thing left that I can think of is the fuel tank pressure sensor.
I hooked up my Autel scanner and got a "fuel tank pressure difference" live reading of between 3.04 and 3.05 Volts at idle. Not sure if that should be that constant or not.
Any help would be much appreciated before I throw $100 at a sensor.
Code P0455 says there is a severe leak. Who performed the smoke test with a negative result?
When codes are set, the monitors go crazy and multiple modules show INC (Incomplete).
Use Autel Scanner and click on monitors and see how many are INC. Leave Autel plugged in and drive at different speeds on streets and hwy and see which ones become OK. You will have to do this multiple times until they are all OK.
I have been following this thread and it's predecessor[ML 430 Purge Solenoid] from the get go. This is my first post on this forum, needless to say I am very impressed with this forum and Maj Dundee, Kohmer et.al. and tried to give a thumbs up to the original thread but I think it didn't register.
Where did you purchase the white cannister a pick and pull?, Its not available for my Sister's ML 320. I assume your "white canister" part is a MB part that fits or is the same as her 320 with a Vin of 4JAB54E6A144038.
I am reluctant to indicate what I have done to date for diagnosing PO442 "small leak" [see post #7 in original thread ] except to say I have yet to do a smoke test and have substituted GM parts for the "white cannister" as I fear I may be criticized for high jacking this thread. My apologies in advance if I have already done so with this post. Chuck
I have a smoke machine which I have tried three different entry points (purge valve, fuel filler neck, and white cannister) and don't see any smoke still.
I'll try to work on the monitors this week.
Chasbe -
Yes I got the canister on ebay.
Edit:
This was the part description on ebay "Mercedes ML320 w163 Purge Valve Fuel Vapor Canister Part # 163476023"
Last edited by norcalcasey; Nov 2, 2020 at 03:54 PM.
Reason: added info on purge canister
P0455 is one of two current codes: I have a code for a faulty oil level sensor that says "range implausible" or something but after looking into it I decided just to leave it for the time being. Dont feel like dropping the pan at the moment. I just unplugged the oil sensor bulb in the cluster and will check the dipstick often.
I'll get back to you with the monitors this evening.
No annual inspections here in IL, so not any time soon.
The code for the Oil light says (P1999 - Oil sensor - oil level and temperature signal implausible)
Still havent had a chance to drive it enough to watch the monitors. The WIS sheet says it checks for fuel tank pressure leakage after 16 minutes of driving.
The code for the Oil light says (P1999 - Oil sensor - oil level and temperature signal implausible)
Still havent had a chance to drive it enough to watch the monitors. The WIS sheet says it checks for fuel tank pressure leakage after 16 minutes of driving.
Code P1999 is not for the Oil Sensor. It is for the right bank O2 sensor after the CAT.
You have two separate codes to deal with, the severe leak and the oil level sensor .
That I understand. Im not going to mess with the oil level sensor as it has a dipstick anyways.
I finally got around to removing the drivers rear splash guard in the wheel well and exposing the top of the fuel pump while I smoke tested. Even shut the garage and turned off the lights so it would be easier to see smoke in my LED flashlight.
Again no leaks!
The only thing left to replace is the EVAP fuel tank pressure sensor
When I unplugged it the EVAP system was still pressurized because I still had it plugged off from the smoke test and I heard a big WHOOOOSH noise meaning the system was holding pressure which is a good sign that I am on the right track.
That I understand. Im not going to mess with the oil level sensor as it has a dipstick anyways.
I finally got around to removing the drivers rear splash guard in the wheel well and exposing the top of the fuel pump while I smoke tested. Even shut the garage and turned off the lights so it would be easier to see smoke in my LED flashlight.
Again no leaks!
The only thing left to replace is the EVAP fuel tank pressure sensor
When I unplugged it the EVAP system was still pressurized because I still had it plugged off from the smoke test and I heard a big WHOOOOSH noise meaning the system was holding pressure which is a good sign that I am on the right track.
Received a call from the dealer stating that they had a bad batch of fuel tank pressure sensors and that they were refunding my money. So I ordered a new one online and installed it.
Drove around for a few days and didn't get any check engine light! I was pretty excited.
Yeah I did. It was with a used unit but it works when I give it 12v on a bench test. Can I test the wiring to make sure the car is getting 12v to it?
Edit: this appears to be related to the new fuel tank pressure sensor. The old unit would measure around 2.8-3.2v and the new one is measuring around 1.8-2.2V
What is the correct reading?
Last edited by norcalcasey; Dec 22, 2020 at 12:31 PM.
I spoke with the Master tech at the dealer and he said p0446 will throw if there's a voltage irregularity with the EVAP system, including the fuel tank pressure sensor.
I mentioned the new code and he said that he toggled the canister with his computer at the dealer and it worked fine. So it's likely not that.
I went back to the old sensor we will see what happens.
I spoke with the Master tech at the dealer and he said p0446 will throw if there's a voltage irregularity with the EVAP system, including the fuel tank pressure sensor.
I mentioned the new code and he said that he toggled the canister with his computer at the dealer and it worked fine. So it's likely not that.
I went back to the old sensor we will see what happens.
Hi,
I am in the same situation with my car like you were in. I have the P0446 fault in my ML. Changed already the purge valve under the hood(oem), changed the charcoal canister shut off valve, checked that there is no broken wire from the x18/3 connector to the shut off valve. The fuel pressure sensor is still the original. Should I change it?
I am very disapponted right now.
Unfortunately, I never found a solution to this! It drives me crazy. I don't know if you have a scan tool, but when I did I could see the fuel pressure sensor change values, so it wasn't broken. I replaced it anyway and saw no change. I smoke tested it 4 times and never any leaks. Incredibly frustrating.
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