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anyone know how to troubleshoot p170 code fuel trim malfunction bank 1?

 

Which subaru what year what engine how many miles. It really is impossible to start to daignose without this information.

 

 

A shot in the dark O2 sensor.

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2000 legacy gt 2.5 limited, 135000miles. P170 code.
Scroll down and read the "Similar Threads". Common problems when P0170 is generated are exhaust leaks, intake leaks, fuel pressure issues (high or low), defective engine coolant temperature sensor (CTS) or intake manifold pressure sensor (or airflow sensor).

 

Basically, the P0170 code indicates the ECU can't compensate enough to get an appropriate A/F mixture. I'd look at the intake first for loose connections, since that's probably the easiest. If you haven't replaced the fuel filter recently, you might consider that. An OBD-II scan tool could be used to determine whether the fuel trims are severely to the rich or lean side, which could help determine a more-likely culprit. Since fuel trims are compensating adjustments, being very rich (positive) means the engine is running lean, while very lean (negative) is an effort to deal with a rich-running condition.

 

None of the above is to say that a bad front O2 sensor isn't causing the problem, but that there are other possibilities.

 

replaced on 2 other times same side, but had a code for it...right side of vehicle. [...]
:confused: Which engine, again?
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Yes, but he also referred to the "side" (not "front" versus "rear"), which would imply an engine that had a sensor for each bank.

 

well the 2.5 has two banks of cylinders :)

 

I've seen it refered to this before, and i am not sure why. It can just be a generic OBDII code for a ailing o2 sensor as opposed to a dead one.

 

SUbaru doesnt have any bank 1 or bank 2 sensors on the 2.5L, but this code does come up on them anyway.

 

nipper

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The code definitions with a 2.5L usually refer to bank 1 sensor 1, or bank 1 sensor 2 -- sensor 1 being the front, and sensor 2 the rear. Bank 2 references would be expected with the 3.0L H-6, since it has a sensor for both bank 1 and bank 2.

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