M-Class (W166) Produced 2012-2015

Smog issue - oxygen sensor heater monitoring

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Old Aug 30, 2020 | 02:22 AM
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immi08's Avatar
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2012 ML350 Bluetec
Smog issue - oxygen sensor heater monitoring

So I’ve had really bad luck with this car. It will not pass smog because the oxygen sensor heater monitor is not ready. I Cleared all codes and drove the car about 500 miles, all codes cleared for smog besides the oxygen sensor heater monitoring. There are no codes showing for any oxygen sensor related items, this is strictly forcing the car to test the oxygen sensor heater to Get to ready/OK state for smog. Given it’s summer and 100 degree weather, I’m not sure if that plays a part in testing but it is quiet hot in California. Any suggestions or tricks to get this code to clear for smog?


Last edited by immi08; Aug 30, 2020 at 04:04 PM.
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Old Aug 30, 2020 | 06:34 PM
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Etienne Lau's Avatar
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Ml350 bluetec
It's not just driving 500 miles that are needed, you may need to have at least 20 restarts to get the OBDII into a ready state.
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Old Aug 30, 2020 | 06:49 PM
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2012 ML350 Bluetec
Originally Posted by Etienne Lau
It's not just driving 500 miles that are needed, you may need to have at least 20 restarts to get the OBDII into a ready state.
my scanner shows 10 drive cycles so I’ll wait a bit longer.
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Old Aug 31, 2020 | 12:51 PM
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While doing some research last night I found out that diesels vehicles above year 2007+ are allowed to have two incomplete monitors. From source:Number of incomplete monitors allowed to pass on diesel powered vehicles:
  • Old standard: any two for 1998 to 2000 model years
  • New standard: zero for 1998 to 2006 (OIS test)
  • Old standard: any one for 2001 & newer model years
  • New standard: any two for 2007 and newer (OIS test

took the car in for smog and passed this AM.
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Old Aug 31, 2020 | 01:02 PM
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Nice! That list you provided depends on the state in question. Here in TX they did not even look at the fact that I had a CEL on my 2014 BT. Texas does not do any emissions testing on any Passenger Diesel Vehicles!!!
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