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PO 171 code system lean bank 1

10-24-2005, 01:34 PM
I tried a search on this and did not find anything to my suprise. Can someone tell me what this code means, What to check. My service engine soon light came on. so i hooked up a code scanner and got this code. I put in a bottle of injector cleaner and cleared the code. It did not come on again for about thirty miles and just when i was getting up to freeway speed on the get on ramp. 98 jimmy 4wd.

Thanks in advance. :confused:

10-24-2005, 03:20 PM
The pcm cannot compensate for what the 02 sensor is perceiving as a lean mixture. Air entering the intake sytem such as a vacuum leak somewhere, low fuel pressure, exhaust leak in front of the sensor, any engine mifire, poorly performing injectors. This will need some one to do a full scan for all sensor inputs and look at the other issues mentioned. Any performance issues?

10-25-2005, 08:10 AM
Not really. I cleared the code again and have about 65 miles on it and it has not shown up yet. Could bad gas or dirty injectors give this code? I have'nt been real good about putting injector cleaner in on a regular basis. I drive 315 miles a week getting back and forth to work.

94 Jimmy
10-25-2005, 12:21 PM
Perhaps a bad O2 sensor.
These sensors are chemical batteries that generate a voltage depending on the level of oxygen in the exharst. They are prone to drift as they age and could be feeding the computer bum dope. The people who make these things say you should replace them every 50,000 miles, that might be too soon but if your having problems you might just change it.
Good Luck

10-25-2005, 05:35 PM
Do you have a K&N or other type of oiled air filter?

P0171 OBD Trouble Code

Technical Description

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.


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 (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled 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. 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

10-26-2005, 06:35 AM
I'll check that stuff out.
I don't have a k&n filter but i think i might get one thats like the stock one. I got about 90 miles on it since i cleared the code and so far so good.

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