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P0170 Fuel Trim Malfunction


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Hi Im hoping someone might know why I get a p0170 "Fuel Trim Malfunction Bank 1" code off an obd2 reader. the check engine light came on on a 100 plus degree day when i had the ac full blast, so i think the motor was running hot. I have taken out and cleaned my mass airflow sensor but it seems that wasnt the problem. I hit some ice this winter and landed on top of a 5 foot snow/ice bank that a flat bed dragged me off. This caused a leak in my flex coupler on my exhaust, which I had someone cut out and weld a new one in. I feel no performance difference other than one instance going 53mph the car shook for a couple seconds. Maybe takes an extra second of cranking to start the engine. please help im trying to solve this without taking out a loan

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Without seeing the vehicle I can only guess but it sounds like you might have an exhaust leak. This causes the O2 sensor to think you have a lean run condition and fattens up the fuel mixture which causes a longterm fuel trim error. This is only a guess but that would also explain the extended crank time. Alternatively, it's possible you might have a fuel pressure issue. Hard to tell without working on the car but I would look at the possibility of an exhaust leak first.

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In thinking about this, it's possible as well you might have an intake manifold leak or leaks at either the throttle body or behind the airflow meter in the intake air boot. What you really need right now is a more than just a code reader, would be nice to get streaming data and find out what the engine is doing...

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  • 4 weeks later...

hello again Im hoping someone might know why my electronic controlled transmission is now stuck in power mode. It turned on by itself and wont turn off no matter how many times i push the button. And frequently when i put the car in reverse the gear display says im in reverse and L (1st gear).

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Well, the mass airflow sensor generates a code of it's own if it's malfunctioning. OTOH, the intake air temp sensor could be an issue although it too should set a code. As for the transmission, I would check the connections to the transmission controller for corrosion and pack them with dielectric grease.

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