Check Engine Light - P173 code comes & goes...
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Super Member
Joined: Apr 2003
Posts: 690
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From: Bay area - California
2000 ML320 2006 SLK 350
Check Engine Light - P173 code comes & goes...
I am not seeking any advice on this topic, but just wanted to share this newest and most recent issue with my ML.
ML320 - 2000 model year - has 108K miles on it. The Check Engine light came on 2 weeks back. Fine, borrowed an OBD reader from Autozone and pulled the codes. Only one code P173 (Fuel trim - bank 2 malfunction).
This is a well discussed topic, and the culprit usually is the MAF, but could also be the fuel filter or CATs or oxygen sensor. I had the CATs replaced at 76K miles and the fuel filter replaced at 94K miles, so those are sort of out of the loop.
Anyways, as I spent 2-3 days thinking about what to do (I have cleaned the MAF in the past at about 65K miles) and wait for a less rainy day to work on my truck, guess what, the Check Engine light went away on its own.
Three days later, it reappeared, same thing P173. Then next day it went away again, and hasn't come back since.
I am waiting for my own OBD II reader that I ordered online (fancy one - bluetooth enabled - lets you read all engine parameters wirelessly on a bluetooth enabled laptop and all that) to arrive in the mail, but in the meantime am just pondering what makes the Check Engine light come and go this way?
What could be making the ECU set/clear P173 on its own?
I guess, either the MAF or an oxygen sensor is in its very initial stages of going out - that's why the fancy OBD reader should help. It also lets you pull sensor voltages and values - that might hold some clues.
Anyone experienced this before?
ML320 - 2000 model year - has 108K miles on it. The Check Engine light came on 2 weeks back. Fine, borrowed an OBD reader from Autozone and pulled the codes. Only one code P173 (Fuel trim - bank 2 malfunction).
This is a well discussed topic, and the culprit usually is the MAF, but could also be the fuel filter or CATs or oxygen sensor. I had the CATs replaced at 76K miles and the fuel filter replaced at 94K miles, so those are sort of out of the loop.
Anyways, as I spent 2-3 days thinking about what to do (I have cleaned the MAF in the past at about 65K miles) and wait for a less rainy day to work on my truck, guess what, the Check Engine light went away on its own.
Three days later, it reappeared, same thing P173. Then next day it went away again, and hasn't come back since.
I am waiting for my own OBD II reader that I ordered online (fancy one - bluetooth enabled - lets you read all engine parameters wirelessly on a bluetooth enabled laptop and all that) to arrive in the mail, but in the meantime am just pondering what makes the Check Engine light come and go this way?
What could be making the ECU set/clear P173 on its own?
I guess, either the MAF or an oxygen sensor is in its very initial stages of going out - that's why the fancy OBD reader should help. It also lets you pull sensor voltages and values - that might hold some clues.
Anyone experienced this before?
Super Member
Joined: Jul 2005
Posts: 717
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From: Manassas, VA, USA
2011 VW cc, 2004 ML350
Thread Starter
Super Member
Joined: Apr 2003
Posts: 690
Likes: 33
From: Bay area - California
2000 ML320 2006 SLK 350
That's what I am guessing too...
In fact, just P173 doesn't point to anything except for a generic adaptation problem. I am going to clean the MAF one more time and see what happens, if not replace it.
It kind of does make sense in a way...MAF issue at 65K miles...reoccurance at 108K miles...near consistent frequency..
It kind of does make sense in a way...MAF issue at 65K miles...reoccurance at 108K miles...near consistent frequency..
Super Member
Joined: Jul 2005
Posts: 717
Likes: 1
From: Manassas, VA, USA
2011 VW cc, 2004 ML350
Our's went south at around 45k miles, fortunately when we were still under warranty. But that damn light would come on then go out, and was never on when I went by the dealer. I kept telling my SA that it was the MAF, but it wasn't until I came in with the light on that they replaced it. I think we had about 85 or 90k on it when we sold it, and the problem had yet to reoccur.
Thread Starter
Super Member
Joined: Apr 2003
Posts: 690
Likes: 33
From: Bay area - California
2000 ML320 2006 SLK 350
Thanks for sharing your experince...
I am convinced now, it is indeed the MAF in my case...will let you know, once I get to cleaning/replacing it this coming weekend.
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Joined: Dec 2007
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From: New England
W212 E350 sport wagon
At 80K - 2001 ML430 - started the same thing. Faults came and went. Cleaned MAF, it all stopped (at least up until 90K now). This P017x fault cluster has been documented from Benz as being a sort of non-problem/problem.
The OBD spec says that if the fault goes away (as seen by the engine) - the CEL light gets turned off after so many engine starts - I forget how many, but it does happen this way as I have seen it for myself.
The OBD spec says that if the fault goes away (as seen by the engine) - the CEL light gets turned off after so many engine starts - I forget how many, but it does happen this way as I have seen it for myself.
