I took the car to fix and they claimed they clean the MAF and everything is ok. I then went home and use my own OBD-II scanner to have a look and found that P173 error code is gone but the P170 is still pending.

The point is they have done something but not completely done. Do I really need to replace the whole MAF to be safe?

Regards,
Michael Tse

MAF cleaning does not always work. I recently cleaned mine after similar codes were triggered, but it did not help. So I replaced it. No codes, runs like a new car. You may want to replace it anyway just to rule it out. You can always throw the old one in the trunk to use as a spare to get you home in case of total MAF failure (it does happen).

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08 W251 R350
97 W210 E320
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86 W126 560SEL
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79 W123 250
78 W123 280E
75 W114 280

Take your point - thanks....