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2001 ML320
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93 Posts
Discussion Starter #1 (Edited)
ML320 throwing P0156 P0141 and P0442 [Edit: and P0161]

Today my 99 ML320 threw:
P0156
P0141
P0442

The truck has 155K and was running with no codes but a bit rough at idle before they showed up. What would be the best way to troubleshoot the problem? I do not have access to freeze frame data but could make a trip to autozone to get it if necessary. Any help is much appreciated. Thanks.
 

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02 ML320 06 ML500
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17,104 Posts
Code P0442 shows that there is a small leak in the Evaporative System. Remove the gas cap and look carefully at the large O-ring. If it is dried and has small cracks in it, it must be replaced. If the cap is OK then you will have to bring the truck to an independent mechanic who has a smoke machine.

Code P0141 is for a faulty heater circuit on the right side after cat. O2 sensor (arrow). That must be replaced.

The other code P0156 is for a faulty 02 sensor on the left side after cat. (bracket). Leave that one alone for now until after you replaced the right side O2 sensor.
 

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2001 ML320
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93 Posts
Discussion Starter #3
Update

The truck threw a P0161 today as well. have not ordered the right side sensor yet. Do I need to replace the left as well?
 
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