clanofwolves
New member
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
Thanks in advance!
Dave
P0171 - System Too Lean Bank 1
- Thread starter clanofwolves
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LittleCaesar
New member
I would start with looking at your live data, particularly your short and long term fuel trims on both banks.
Oxygen sensors original?
Oxygen sensors original?
clanofwolves
New member
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?
19963.4lsr5
New member
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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What is your MAF reading at idle? That will help indicate if you have a vacuum leak.....
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19963.4lsr5
New member
LittleCaesar
New member
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....
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....
clanofwolves
New member
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?
clanofwolves
New member
What should the MAF number be if she's working correctly?
clanofwolves
New member
Haha, chocolate iced custard filled hopefully... you betting the upstream one?
Yes.....If ur gonna replace one...i would do both....same code..then shorty after bank 2 code came up..
Last edited:
19963.4lsr5
New member
.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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Joelzy
New member
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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thegipper
New member
O2 sensors don't always throw a code when they go bad. If your O2 sensors are original, I'd replace them. It's likely the issue causing your P0171 and even if it isn't, they are due to be replaced. You'll probably pick up a mpg or two (I did when I replaced mine due to a P0172 too rich code).
Good luck
clanofwolves
New member
Here is the data my Foxwell gives me at idle:
MAF sensor could be skewed and reading incorrectly even if it is clean. Same with the upstream oxygen sensor (air/fuel sensor). If it's readings are skewed, but it's still varying voltage you most likely won't set an oxygen sensor code.
FYI: Upstream oxygen (air/fuel) sensor tells the ecm the data necessary to adjust your fuel trims. The downstream oxygen sensor monitors catalytic converter efficiency.
Try to get live data after the engine has warmed up and the idle has dropped down to around 600 rpms +/-100 rpm
19963.4lsr5
New member
Here is the data my Foxwell gives me at idle:
You need to repost the results after the engine is fully warmed up. Include rpm and TPS.
Try and switch your readings to American measurements if you can.
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