Check engine light P0170 and P0173 - Page 2 - PeachParts Mercedes-Benz Forum

sdanville · #1 01-08-2007, 09:17 PM

Gilly- I cannot tell you how long it took me to find this post.
quote: In over 90% of these 2 codes, it's the mass air flow sensor. Other 10% it's a vacuum leak, usually in the induction system after the mass air flow sensor. You could also look for a huge blockage in the filter box, we had one once where mice or squirrels attempted to build a nest in the bottom of the air filter box, which realy plugged the airflow. Ran bad too though and had these codes. Pretty confident it's the mass airflow sensor though.

I bought not one but 2 sensors thinking the 1st was a cheap $90 ebay chineese one. replaced the plugs..paid a pro $90 claiming he found a wrongly routed vacuum line..
then reading your post i sprayed starting fluid around the mass of vacuum lines in the back of my engine near the firewall and heard the RPM's pick up.
It took another 50 minutes with mirror and flashlight to find a gizmo came out of its hole to the intake manifold. Just wanted to thank you. Steve.

fema · #2 01-15-2007, 07:24 PM

I may have the same problem and wanted to get an opinion here (my search function for other simlar posts doesn't seem to be working):

In the fall the Check Engine light came on intermittently and finally stayed off until now. Also, a couple of times lately the Fuel Reserve light blinks; this also happened to me once in the fall. As well of late, the car will crank with the key released in the on position, but not start - never heard any car act like this, engine cranking but clearly not going to start and key released.

Coincidentally this week the weather has been super cold, neg 15 last night, and the car does stay outside all year long. There was rough running yesterday morning, and today it would stall when put in gear until a few minutes warm up. Then it ran fine, check engine light still on.

Since I am 3 hours from a dealer, I will take it to the local guy this week to check codes but in the meantime wondering if anyone has a clue - thanks.

sdanville · #3 01-15-2007, 07:28 PM

The only time my ML320 would stall and maybe start up or maybe not start back up..was the cranksthaft position sensor. One bolt to replace.
I paid about $75 online.

Yours sounds like maybe a fuel pressure check is needed.

fema · #4 01-15-2007, 07:40 PM

Is this something that will come up when the mechanic checks the codes? Whiel I've been doing more and more of my own work on the vehicle, I don't have a code reader I hate to start replacing stuff by trial and error.

On the other hand, if it is a maintenance item to replace certain sensors preiodiclly I don't mind going in there and doing this - I have 128K miles and am the original owner. Are there certain "easy" ones to replace like the CPR?

sdanville · #5 01-15-2007, 07:50 PM

you can buy a code reader for $50 on ebay.
I bought mine at sears for $79.

I do not know if it will tell you what your problem is.

My last codes were just mis fires. but reading the forums pointed to MAS or vacuum leak.
I still have a rough idle. its been 2 months now i cant figure it all out.

in terms of easy to fix. search these forums for instrustions and most everything is easy to fix if you have courage and good light.

fema · #6 01-16-2007, 10:11 AM

Good deal, thanks guys - I will check it out. Didn't know Auto Zone would do this for free either!