P0455 and P0456 solved...
 

I've been having these two codes for a little while. They were accompanied with the fuel reserve light flashing, which "normally" indicates a loose gas cap. However, the gas cap is tight and all the evap system valves seem to be functioning normally.

Took it in to my indie for an SDS hook up, but before connecting it, he knew what the problem was. The fuel level sensor is also part of the evap system and will cause the symptoms. And so the SDS confirmed.

Anyway, replaced both as the tank had to be drained anyway. Problem solved.

Car: 1998 C230, M111 aspro engine. Mileage: 202,000

My idie mechanic could not find any problem with the evap system; for the same P0455 eror code. This was back in ealy July. Per his suggestion I have been keeping the fuel between 1/4 and 3/4 without any incident. Sunday I filled to about 7/8 and at a stop light on Monday the low fuel light came on again. Went out with engine restart; came on again at next light and now CEL is on. Could this be the low fuel sensor/ fuel lever sensor? Do you have part numbers for the items you replaced to get your system to work correctly? Is the tank difficult to take off in replace the sensor?

It's not hat big of a job, actually. The sensors (one for each half of the "saddle" tank) are accessed through the rear seat and you don't take the tank out of the car. You do have to drain the gas, however.

I didn't want to muck about so I had my mechanic do it, and it's a reaonable 1.8 hours labour to drain/fill the tank and R&R both sensors. One (I think the right) is the culprit, but it would be nuts not to do both.

I don't have the parts numbers handy, but Fastlane sells them as they're a common replacement part on W202 cars.

The trick in the repair is knowing that the sensor is part of the evap system and it can cause a leak in the system, meaning the flashing reserve light and eventual CEL. You check the other valves first, and if they're working, then odds are it's the fuel level sensor.

The 202 fuel sensors are found UNDER the car, you remove a small plastic plate on each side at the forward edge of the tank. There are special pipes that can be attached to the sensors which open a ball valve which allows the tank to be pressurized and blows out the fuel into a fuel caddy. IIRC the drivers side (left) contains the pressure sensor, the opposite side is only for level sensing. I agree, usually best doing them in pairs, but only one side is used for the evap system (pressure sensing). There may also be a bulletin about updated parts requiring both to be replaced.
Gilly

It's good thing I had my mechanic do the job! I would have looked in the wrong spot...

IIRC the sensors for the W203 are accessed from inside, not the 202 tho.
Gilly