12-30-2020, 01:58 PM
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#1
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P0171 - System Too Lean Bank 1
Check engine light came on, my Foxwell is telling me "P0171 - System Too Lean Bank 1". What do you guys think is the cause is as I start an investigation.
Thanks in advance!
Dave
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12-30-2020, 02:37 PM
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#2
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I would start with looking at your live data, particularly your short and long term fuel trims on both banks.
Oxygen sensors original?
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12-30-2020, 03:16 PM
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#3
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Old oxygen sensors, vacuum leak, dirty MAF. Likely culprits to check in that order.
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12-30-2020, 06:10 PM
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#4
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Quote:
Originally Posted by LittleCaesar
I would start with looking at your live data, particularly your short and long term fuel trims on both banks.
Oxygen sensors original?
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Yes, best I know (second owner from 2011) the O2 sensors are original.
I'm looking at the live data function and trying to figure out what Foxwell indicates as fuel trim. Any ideas on what they would deem this on the live data list?
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12-30-2020, 06:26 PM
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#5
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If you can get a freeze frame when it the code shown up it would be helpful.
What is your MAF reading at idle? That will help indicate if you have a vacuum leak.....
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12-30-2020, 06:27 PM
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#6
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Quote:
Originally Posted by clanofwolves
Yes, best I know (second owner from 2011) the O2 sensors are original.
I'm looking at the live data function and trying to figure out what Foxwell indicates as fuel trim. Any ideas on what they would deem this on the live data list?
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LTFT is the important one. Plus MAF at idle.
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12-30-2020, 06:42 PM
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#7
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A dollar to a donut (lol)....oxygen sensor
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12-30-2020, 06:42 PM
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#8
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If you go to the main menu function, it should be the oxygen sensor test, probably either the 4th, 5th, or 6th test. You should see stft and lgft numbers. You would like to see those values as close to zero as possible, but given the code, some will not be.
As stated above, there should be a freeze frame function on the live data main menu. It shows the values of sensors and the like when the ECU sees the fault occur, which may give insight into what caused the money light to come on.
Having never used Foxwell I couldn’t say for certain concerning the live data main menu but usually all OBDII scanners follow the same set list....
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12-30-2020, 06:50 PM
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#9
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Quote:
Originally Posted by Bad Luck
Old oxygen sensors, vacuum leak, dirty MAF. Likely culprits to check in that order.
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I did check for vacuum leaks first thing visually as well as using starter fluid, none detected.
The O2 sensors are original as far as I know, but wouldn't they too throw a code in addition to the P0171?
I remove and clean the MAF every 20,000 miles and I just did it about 5K ago, but maybe it is an issue anyway?
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12-30-2020, 06:52 PM
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#10
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Quote:
Originally Posted by 19963.4lsr5
LTFT is the important one. Plus MAF at idle.
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What should the MAF number be if she's working correctly?
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12-30-2020, 06:55 PM
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#11
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Quote:
Originally Posted by bear1998
A dollar to a donut (lol)....oxygen sensor
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Haha, chocolate iced custard filled hopefully... you betting the upstream one?
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12-30-2020, 07:14 PM
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#12
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Quote:
Originally Posted by clanofwolves
Haha, chocolate iced custard filled hopefully... you betting the upstream one?
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Yes.....If ur gonna replace one...i would do both....same code..then shorty after bank 2 code came up..
Last edited by bear1998; 12-30-2020 at 07:19 PM.
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12-31-2020, 12:06 AM
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#13
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Quote:
Originally Posted by clanofwolves
What should the MAF number be if she's working correctly?
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.518 lbs/min is a good number at a warmed up 700rpm idle. Anything less is a vacuum leak.
I created a thread in 2019 about the subject when I put my rebuilt engine in and had your code at idle.
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12-31-2020, 02:04 AM
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#14
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Don't forget to clean your IAC. I'm putting mine back together tomorrow.
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12-31-2020, 02:14 AM
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#15
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I went through this after my rebuild and chased it for a while. ended up being a vac leak at an injector seal which was one of the few things i didnt change during the rebuild because i forgot them and didnt want to wait anymore. Got to wait anyhow
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