Hey all,
Got a check engine light on my C250. The code is P0456 which is a very small leak in the EVAP emission control system.

After some Googling, I found that the usual suspects are, gas cap, EVAP purge solenoid valve, Charcoal canister I already replaced the gas cap, but that didn’t fix it. Planning to replace the purge valve next.

Anyone dealt with this before? Any suggestions on what else to look for or check before moving on to the charcoal canister?

Appreciate any input!

C250 2013
146 K miles

 

I have the M272 engine and when my purge valve failed I had trouble starting the car right after getting gas, would just crank and crank. I figured out that pushing the gas pedal to the floor would get it to start. I was also getting a check engine light, I forget what the fault code was but P0456 doesnt sound familiar.

To check the purge valve it should start clicking and making a ticking sound shortly after starting the car which means its operating. Should be able to hear it ticking and feel it with your finger on it. Its the valve opening and closing quickly.

When I replaced mine I wasnt too sure if it was the issue, didnt know much about how it works. I bought an inexpensive used purge valve from an older SLK which does cross reference with the same part numbers, it was just a much bigger purge valve. It did fix the issue and the check wngine light but it was very loud and could hear it ticking away from the drivers seat. I have since replaced it again with a new purge valve i came across for a good price on eBay. Replaced it last year and its working great.

Im guessing you have the M271 engine. I dont have that manual handy but looking thru for the M272 theres info on the evap system. May be helpful to diagnose the issue. Not sure which specific purge valve you have in there, i'll show the exact one I bought.

 

Thanks @TimC300
I replaced the purge valve and cleared the code. Drove the car to work yesterday, about 70 miles round trip, so far the code did not re-appear, fingers crossed.
The purge valve was bit pricey, $116.00 but no complaints.

 

I have had this code pop up every few months on my CLK.

Replaced seal on gas cap, it still reappears. It has a skill for popping up on SMOG years.