MrMustard

Hey guys!

Felt like it was time to finally make a post about this. I've been getting a CEL pop every so often (actually it's always happening when it's muggy/humid/rainy outside), 4 times now to be precious, for the P0453 code. The code is for Evaporative Emission Control System Pressure Sensor High Input, so after researching I found it could be a few things. Possibly a leak from the gas cap - so I replaced that seal. It could also be the emissions purge value sticking - so I bought a new one and plan to put it on tomorrow. My only other shot at this is the actual fuel sending unit pressure switch which I believe is mounted above the access port to the tank.

Has anyone else had this issue and been able to correct it? So far there are no performance changes other than an annoying orange CEL light which reallllly irritates my OCD




Any suggestions would be great!

Plutoe

Yea,when it stops raining change the sensor or leave it alone like you have and the CEL bulb will eventually burn out which will be more expenses!!

MrMustard

Installed the new valve. Hardest part was trying to uncrimp the hose clamp but once I figured that out it was a breeze. Let's hope for the best. Will reply with results after driving

kbob999

I did a quick search and found results pointing to the pressure sensor as the potential culprit. I believe it is part of the fuel tank level sensor.

The purge valve simply allows the opening of the charcoal canister venting to the engine during vacuum conditions. If it were not working right, you would suspect high pressure (due to fuel expansion) when closed (high reading); or near constant vacuum conditions if always open (low reading, or other errors). Just a theory of mine, not expert advice.

On my SL55 I have replaced all of the following chasing a vacuum leak (P0455) at my engine: Fuel level and sensor; purge valve; charcoal canister; fuel cap. None were the problem, it was a loose vacuum line to the purge valve where it enters the intake manifold.

MrMustard

Thanks for the suggestion, I replaced the purge valve with the assumption that if there's too much pressure in the line then something is clogged or not opening. From what I've read, it looks like my next stop will be checking the wires to the sending unit - I saw a few threads saying the harness could be fried, or the pressure sensor is shot, which apparently like you said, is in the sending unit with the fuel filter sock in the tank - it's called a "mounting plate" when it's really the entire unit.


Part #10
MB PN#2034701641

MrMustard

Well, the CEL came back. So the gas cap seal and the new purge valve did not do the trick. Going to take the rear seat put this weekend to investigate the wiring and make sure I order the right part. I found this DIY for a w203 on the sending unit replacement.. However I keep seeing part numbers for a pressure sensor (though it's not listed in the diagram above) so I'm not 100% certain if it's built in or not, my guess is the sending unit and pressure sensor are one unit.
http://installuniversity.com/mb/w203/w203/fp.html


Edit: Found a star search, looks like it's one unit >.<

MrMustard

So I confirmed that my car has the sensor built into the sending unit. Here's a picture for reference, 2006 US spec C55 AMG



I cleaned up the wiring and noticed some of the wires weren't in the protector bracket thing so I fixed that. Will hook a multimeter to make sure it's not burnt up. If the cel comes back I'll be ordering a new sending unit.

Maffu313

I've done quite a bit of research on this as well, best threat I could find was this:

https://mbworld.org/forums/c32-amg-c...005-c55-2.html

Seems that it's a relatively common problem; the link provides a DIY that you could try for much cheaper before ordering a new sending unit as the last resort.

MrMustard

Update after driving for a week:
The cel hasn't come back, I have a sneaking suspicion that the cause of the cel was not the fuel tank pressure sensor, but the wiring going to it. If you look at the image in my last post you can see the bundle of wiring exiting the fuel tank chamber through a slit, well these wires were not in their original position and seemed like they were been squashed by the cover that is bolted down. In addition the flat wiring harness protection sheath was actually crushing the wiring since whoever touched this last didn't put the wiring back into the protector.

Anyway, I believe this case has been solved - so if you have the P0453 code, check your harness at the fuel pump!!

MrMustard

Well it came back again. Snapped a pic of the sending unit

Sending unit
A2094700241 (includes pressure sensor - I believe this P/n has been superseded)


Pressure sensor had a part number on top. A0015421118 but it not possible to order it. The left side sending is one piece.

I followed the advice on a YouTube video to prove the wiring is good.
5v Ref = 5v constant
Signal = ~4.75v fluctuating

Jumped signal to ground and saw 0.00v
Jumped 5v ref to signal and saw 5.00v

This proves ground and signal wire are working, so now I have to either do a vacuum test on the tank to see if there's a leak.. Though in my case, high pressure or voltage would indicate there's a blockage rather than a leak.. More than likely the pressure sensor is fried.

It seems p/n 2034701641 should fit according to this


Found it at ecstuning for a good deal:
https://www.ecstuning.com/Search/2034701641/ES2897464/

MrMustard

So the previously mentioned part number is not correct. Those have two fuel ports instead of only one so it is NOT compatible.

I was able to do more research and found the compatible p/n to be 2094700494 - problem is the newer style sending unit uses a different harness plug. Luckily this can easily be changed.

Backstory:
So I got luckily and found someone selling a used sending unit out of a C55 AMG.. however it used a w209 part number. I took a chance considering the price and figured it couldn't hurt.. Plus it looked in pretty great condition. I looked it up on multiple sites MB sites and found it did indeed cross reference the c55, among other models. This p/n also seems to come with an updated pressure sensor which IS removable.. So if this ever happens again - unlikely - I can replace a 100% generic $10 part instead of $350+ for the entire sending unit.





**You'll notice that the pressure sensor will now require a new connector for it to work. Luckily this sensor is a generic build of a GM 3 wire pressure sensor and pigtails are readily available.
The p/n for this particular plug is PT2782



Note the location of the slot, this corresponds to the female side.


Wiring conversion will be a simple swap of plugs, will try without cutting anything first
Oem color = Description = New Plug color
A) Brown = Ground = Black
B) Blue/purple = Signal = Green
C) Orange/Yellow = 5v ref = Grey

MrMustard

I was successfully able to swap the sending units out as well as change the pressure sensor plug over to the GM style one - had to cut the old one off and solder the new one on.

tips:
-When unplugging the single hose on top of the sending unit. Make sure you have plenty of rags, fuel will shoot out this at high pressure.
-When routing the new lines across the hump, there's a small loop inside the gas tank you'll have to initially thread the hoses through, it's pretty large and easy to find
-The hose that is clipped into the fuel pump on the passenger side requires you to press a small slim button. Feel around the bottom of the plug and press in, you'll be able to then release the hose.
-One of the new lines will be a larger diameter, and won't fit into the original housing, you'll have to wrap to essentially just leave it there hanging - try to support it by leaving it where it *should clip into
Overall it's been a success for me, real test will be driving it more and checking for leaks after I fill up.

I used this guide as a reference, even though it's for a W211, the steps were the same.
http://www.pelicanparts.com/techarti...eplacement.htm

Edit: after driving a few hours and checking for leaks, I can say that I believe I have fixed the stupid CEL. Unfortunately I wasn't quick enough when I pulled the high pressure hose off and I sprayed fuel over the bottoms of my rear seats. Used dish soap and water to get what I could and then put a bit of ground coffee beans around the neck to aid in soaking up the remaining smell. Will have to vacuum this out later but it'll help for now.