Fuel Trim Malfunction

[Marz740il]

Check Engine light, ran an OBD-II Scan and it came back Fuel Trim Malfunction (Bank 1 and Bank 2). Anyone know how to corner this problem and eliminate it?

Mike

[lincolnmaster80]

I'm guessing your mixture is too lean and it's possibly running a bit rough and there isn't enough fuel getting to the engine. A rich mixture is too much fuel, but that error is usually related to O2 sensors. It might be the O2, but 'trim malfunction,' you're looking at a vacuum leak. Check the oil seperator valve then the throttle body gasket and then the intakes. Most likely a vacuum leak and the throttle body, oil seperator and intake are the most likely. Run your hand around the bottom of the throttle body and oil seperator, if it's greasy/oily there, there's a leak.

If there is no leak, test the MAF sensors...they might need cleaning, and in a worst case senario, might need replacing.

[ryunk]

In my case it is not a vacuum leak. I currently have the Fuel Trim Malfunction codes for both banks and it is in the shop now. The mechanic verified it is not a vacuum leak. His suspicion is that it is a bad Air Mass Meter because the voltage readings are not what they should be, during an instrumented test drive. He did not have a new Air Mass meter to verify today. I will know tomorrow if this is correct.

The Air Mass Meter was replaced and it runs great, much more power. No more Fuel Trim Malfunction codes.