Check engine codes P0170 and P0173 Fix
Thread Starter
Junior Member
Joined: Oct 2007
Posts: 62
Likes: 14
From: Philadelphia, PA
2014 E550 4Matic
Check engine codes P0170 and P0173 Fix
I recently performed the "B" service on a 2008 W204 C300, including changing the air filters. That was a couple weeks ago. Then just yesterday, I noticed a check engine light.
I pulled the codes and found P0170 and P0173, fuel trim left bank and right bank (don't know which one is which). I also noticed that the car seemed to have a slightly unsteady idle- normally it's rock solid and steady rpm.
Doing some research here, a lot of people have had issues with these codes pointing to forgetting the secondary air pump hose on the front of the airbox.
Well that was not the case in my instance. The airbox to MAF connection was somehow not seated properly, so the airbox could be easily pulled off the MAF with just light pressure from my fingertips. Obviously that was not right.
Pulled the airbox off, connected the airhoses on the front of the airbox first (these are always tricky to reattach because they're stiff). Then I connected the secondary air pump hose (the one with the big arrow on the hose and matching arrow on the airbox). Finally, I reseated the airbox to MAF connection by pressing firmly down, making sure the clips seated properly and then seeing if it moved under light pressure. I got it firmly seated, airbox does not move now, all connections are tight.
Restarted the car, idle is smooth again, problem solved. It will take some drive cycles for the check engine light to turn off.
I pulled the codes and found P0170 and P0173, fuel trim left bank and right bank (don't know which one is which). I also noticed that the car seemed to have a slightly unsteady idle- normally it's rock solid and steady rpm.
Doing some research here, a lot of people have had issues with these codes pointing to forgetting the secondary air pump hose on the front of the airbox.
Well that was not the case in my instance. The airbox to MAF connection was somehow not seated properly, so the airbox could be easily pulled off the MAF with just light pressure from my fingertips. Obviously that was not right.
Pulled the airbox off, connected the airhoses on the front of the airbox first (these are always tricky to reattach because they're stiff). Then I connected the secondary air pump hose (the one with the big arrow on the hose and matching arrow on the airbox). Finally, I reseated the airbox to MAF connection by pressing firmly down, making sure the clips seated properly and then seeing if it moved under light pressure. I got it firmly seated, airbox does not move now, all connections are tight.
Restarted the car, idle is smooth again, problem solved. It will take some drive cycles for the check engine light to turn off.
Junior Member
Joined: Apr 2018
Posts: 35
Likes: 3
From: Lady of Liberty
08 c300 sport
Hello CleanerPA,
Has the CEL finally been gone for good? I have been head on whith
these P0170 and P0173 for the last 2 months with not much luck.
I noticed your car is a Luxury 4matic which has a Clamping Piece
(round wire metal clip almost has a shape of a horse shoe)
which suppose to clip over the air cleaner box when it is
properly seated....In my case, the car is a Sport model
I purchased it used and noticed that there was never a Clip
on my air cleaner box thus it is hard for me to tell if
my air box is seated properly.....Car is being used as
daily commuter with the CEL on latest codes are
P0170 and P0173, thank you all.
Has the CEL finally been gone for good? I have been head on whith
these P0170 and P0173 for the last 2 months with not much luck.
I noticed your car is a Luxury 4matic which has a Clamping Piece
(round wire metal clip almost has a shape of a horse shoe)
which suppose to clip over the air cleaner box when it is
properly seated....In my case, the car is a Sport model
I purchased it used and noticed that there was never a Clip
on my air cleaner box thus it is hard for me to tell if
my air box is seated properly.....Car is being used as
daily commuter with the CEL on latest codes are
P0170 and P0173, thank you all.
Junior Member
Joined: Apr 2018
Posts: 35
Likes: 3
From: Lady of Liberty
08 c300 sport
Itwargssf, thank you for your reply, this video helped me
to understand better how crucial it is for the air cleaner box
to be installed properly but my problem is I could not Swing
over that Clip simply because it was a bit toooooo short
thus it made me think that I may not have it properly
seated, anymore help please and thank you.
to understand better how crucial it is for the air cleaner box
to be installed properly but my problem is I could not Swing
over that Clip simply because it was a bit toooooo short
thus it made me think that I may not have it properly
seated, anymore help please and thank you.
Super Member
Joined: Jun 2017
Posts: 608
Likes: 107
From: Western NC
2009 MB C300 Sport 4matic
Itwargssf, thank you for your reply, this video helped me
to understand better how crucial it is for the air cleaner box
to be installed properly but my problem is I could not Swing
over that Clip simply because it was a bit toooooo short
thus it made me think that I may not have it properly
seated, anymore help please and thank you.
to understand better how crucial it is for the air cleaner box
to be installed properly but my problem is I could not Swing
over that Clip simply because it was a bit toooooo short
thus it made me think that I may not have it properly
seated, anymore help please and thank you.
Did I misunderstand....thought you said your clip was missing ( as is mine). The both banks lean code can also mean the evap purge solenoid/valve is stuck open.. This will cause a lean condition as the open valve keeps drawing air (unmetered)into the IM. . Easy to check..do a Search for its location (driver's side engine compartment underneath the fabric intake hose. ...one electrical connector and 2 hoses and easy off rubber mount. You have to get new hose clamps, the little guys, to reattach hoses..others claim reusable with special pinch pliers but I used small fuel hose clamps. If interested in checking your EVAP PURGE, remove the unit with hoses/connector off and try to blow through one of the hose inlets...if no air passes "good to Go", if you can blow air through, it's stuck OPEN. A controlled "whack" with a screwdriver handle unstuck mine and it worked codelessly for 2 weeks before the not expensive replacement showed up. Before that I'd have to erase the CEL codes every day or so.
Junior Member
Joined: Apr 2018
Posts: 35
Likes: 3
From: Lady of Liberty
08 c300 sport
Did I misunderstand....thought you said your clip was missing ( as is mine). The both banks lean censode can also mean the evap purge solenoid/valve is stuck open.. This will cause a lean condition as the open valve keeps drawing air (unmetered)into the IM. . Easy to check..do a Search for its location (driver's side engine compartment underneath the fabric intake hose. ...one electrical connector and 2 hoses and easy off rubber mount. You have to get new hose clamps, the little guys, to reattach hoses..others claim reusable with special pinch pliers but I used small fuel hose clamps. If interested in checking your EVAP PURGE, remove the unit with hoses/connector off and try to blow through one of the hose inlets...if no air passes "good to Go", if you can blow air through, it's stuck OPEN. A controlled "whack" with a screwdriver handle unstuck mine and it worked codelessly for 2 weeks before the not expensive replacement showed up. Before that I'd have to erase the CEL codes every day or so.
part number is A 272 142 00 12 and it is named Clamping Piece when ready to put it on....it was a about half an inch tooooo short
for it to clip to the air box....made me mad so I just left it unhooked behind the MAF sensor.
Something still bothers me that if this car ever had a factory installed Clip....errrrr.
Car seems to run perfectly normal even if the CEL has been on the whole episode.
The indy shop recommanded changing vacuum hoses though.
