I have a 2000 ML 320 with 102k miles with the following codes, PO300, 301, 302, 303, PO130 and PO 135. The plugs were replaced with factory plugs at 60k and the wires and O2 sensors are original. Should I just replace the one sensor, plugs and wires or both front sensors due to mileage. Also since it all is Bank 1 related is there anything else that is suspect such as the cat on that side. It doesn't seem to have a lot of pep and the mpg is down to about 14 in town.

Has the catalyst recall been done??

If you truck doesn't fall into that recall have the exhaust back pressure checked on the passenger side.

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Thanks Doc, I will check with the dealer about the recall.

Just checked with the dealer and both cats were replaced at 75k miles Sept 05. Guess i will do the tuneup and see if lights stay out.

check the back pressure on bank 1 even though the cats have been changed the can still be bad this is a mb. po130& 135 are both o2 codes right? there isnt much else that will cause misfires on just one bank that would also affect all the cylinders on that bank