My check engine light also came on after my oil was changed and new spark plugs were installed on my 2001 E320 with 49098 miles. The OBD check indicated code PO 170 -fuel trim malfunction -bank number 1. The gas cap is ok . Any idea what to do next

lvalario- It could be almost anything. No point in guessing. Take the car to most any auto parts store, and they will read the trouble codes for free. Write down the exact trouble codes and post them here. Someone might be able to point you in the right direction.

-GH

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I would remove and clean the MAF. Usually when the MAF needs this, you get P0170 and P0173 but it could not hurt. Just be sure to use CRC Mass Airflow Sensor cleaner. Also make sure none of the plastic "pipes" that run from the air filter box are cracked or broken. This could trigger P0170 or at least it did on one of my previous MB's.