View Full Version : trouble code p0171

02-25-2010, 02:05 PM
hey tim thanks for help today , met you today @ checker, you read the code on the tacoma. I forgot your user name but again thanks.

P0171 OBD-II Trouble Code


System Too Lean (Bank 1)
What does that mean?

Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0174, and in fact your vehicle may show both codes at the same time.

You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.
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A code P0171 may mean that one or more of the following has happened:

* The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
* There could be a vacuum leak downstream of the MAF sensor.

Possible Solutions

Possible solutions include:

* In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
* Inspect all vacuum and PCV hoses, replace if necessary
* Check for a dirty fuel filter and proper fuel pressure

02-25-2010, 04:00 PM
Hey Lars, great to meet you.. so do you have a K&N filter? If so my advice would be to get rid of that thing, that oil is clogging up your MAF sensor. your engine is the 3.4 V6, right?

I'm sure someone smarter than I will pipe in with better suggestions... :) :beer:

02-25-2010, 04:50 PM
Tim has a good point, over oiled K&N's can cause problems on MAF equipped vehicles. It happened to me in my 60 with a 5.3 Vortec. You can buy MAF cleaner spray from NAPA or other places. CrC makes it. use the MAF spray though, not carb or brake cleaner... those two supposedly can harm the sensor.

02-25-2010, 05:37 PM
I have successfully been running a K&N (with a foam overfilter) with being sure to not over oil it. That said, I am about to clean my MAF with the aforementioned cleaner, from Checkers, but mostly due to the fine dust I found on it. :rant:

02-26-2010, 12:36 PM
this is my wifes older sons truck, a toyota tacoma prerunner, and no it does not have a k&n filter. I think it is just dirty, 135000 miles on it. I have not done anything to the maf, going to wait for the cel to come back. the crc quick clean works pretty good, i get it from work. I own a 2000 toyota tundra limited with a k&n filter and have had no problems just don't over oil it.

02-26-2010, 10:31 PM
nothing wrong with k&n just use common sense.. and yes only use MAF cleaner. brake and carb cleneer WILL distroy the sensor.. but you can get that p0171 from bad oxygen sensors also.