benbac

So the car is aging a bit and the check engine light keeps popping up, this time around, i'm told it's both the upstream o2 sensors and fuel tank pressure sensors.

I can locate the o2 sensors, i just don't know which one is the upstream, can anyone help me identify/confirm it? (I'm assuming Bank 1 Sensor 1, Bank 2 Sensor 1)

As for the fuel tank pressure sensor, I'm assuming it's part # A1635422818, 1635422818 and that it's just a basic swap in one of the wheel wells (not actually touching the fuel tank)
I'm just not familiar where it's located, can anyone help with this?

In addition, i'm also swapping out the front right air strut (it started sagging)
Another expense
i wonder if it's time to get another car?

konigstiger

benbac

Dan the man! you're too quick!!!

benbac

As for the fuel tank pressure sensor, 1635422818, is it in the same location / process as the S550 in the rear right wheel well?

konigstiger

Check top of fuel pump located rear seat, driver side.

Ivan-2019

konigstiger, you are indeed the man!

I believe I have replaced almost the entire EVAP system. Started with a P0456. Replaced the gas cap...no change. Replaced shut of switch...no change. Replaced the charcoal canister...that fixed it! Then a couple weeks later, P0446. Replaced the purge valve...fixed that for a couple weeks. Then got the big read red gas cap warning and a P0451...opened the fuel filler door and the (obviously) defective gas cap I had already replaced came apart in 3 pieces. So I limped it home, ordered another gas cap, replaced that, cleared the codes and all was well....for a couple of weeks. Then I got hit with another red gas cap warning, all of those codes again, and this time a P0451 to go with it. Is it possible most of these EVAP gremlins I've been chasing has been the pressure sensor?

konigstiger

What have you got to loose (part # 1635422818)?
https://www.autocodes.com/p0451_mercedes-benz.html#fix

Ivan-2019

Right now, it looks like I have about $25.41 to lose

So if I'm looking at this right, I don't need to yank the fuel pump?

konigstiger

No however, the fuel tank must only be filled to a maximum of a 75% otherwise the fuel may finds its way into the vehicle interior use an absorbent rag to collect any escaping fuel.

benbac

So I just looked under the seat at the fuel sending unit top and it doesn't seem to look like what was previously pictured. Any ideas here? Do I need a different part? Is the sensor located elsewhere?

benbac

The harness doesn't look to be compatible with the sensor, ideas? 🤔

konigstiger

FPS is integrated into pump. Original pump 2114701541 (yours) FPS is not replaceable and is replaced by current part 2114706094 requiring additional 2114400507 harness that incorporates replaceable FPS.

benbac

Thanks for this konigstiger!!!!!
Considering i'm replacing the Fuel Sender unit (2114706094), which still requires disconnecting from the Fuel Pump (2114704194) on the other side of the tank, I'm wondering if I should just go ahead and replace that as well since it's all getting exposed/coming out? opinion?
And if i'm going to replace the Fuel Pump on the other side, is 2114704194 the correct part #? and is there anything else that I may need?

konigstiger

Confirmed for your VIN: M3 = 2114702994, 55/1 = 2114706094 + 2114400507 harness your call on replacement - was it ever replaced, cost...

benbac

Never been replaced, now is probably as good a time as any

Thanks for everything!