P0171 Error Code - Help!
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Junior Member
Joined: Nov 2001
Posts: 3
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From: Michigan
P0171 Error Code - Help!
Hello Fellow F150 Owners:
I have a 1997 F150 Supercab 4X4 with the 4.6L V8. The truck has 110,000 miles. At about 100,000 miles, the check engine light came on and showed error codes P0171 and P0174, engine running too lean.
At that time, I changed the O2 sensors, spark plugs/wires, air filter, oil, fuel filter, and PCV. I also changed the DPFE sensor. The truck was ok for a while but the check engine light popped back on shortly after that. I have been so busy that I could not rent the scanner again and check the code until now.
The scanner still shows a code of P0171, bank 1 running too lean. I assume Bank 1 is the driver side. Looking at the O2 sensor data, the #1 sensors for both banks appear normal, meaning they fluctuate between lean and rich. The bank 1 #2 sensor which I assume is the sensor farthest from the engine on the drivers side is reading a constant rich at idle (volts about 0.6 to 0.7) Bank 2 #2 is reading constant lean (volts about 0.2) at idle.
When I changed the plugs, I noticed one plug on the drivers side had what appeared to be a buildup of sand/dirt around it. I could not change it and figured I would do it later. I have not changed it yet. I realize that was a mistake, but I figured 7/8 was better than 0/8 and I was leaving for vacation the next day. Maybe that plug is not burning all the fuel causing the one cylinder to send unburned gas through to the exhaust?
Does anyone have any thoughts on what might be causing this light to stay on with code P0171? Maybe I just need to have that plug changed?
Any and all help is appreciated. Thanks!
Andrew Lewandowski
I have a 1997 F150 Supercab 4X4 with the 4.6L V8. The truck has 110,000 miles. At about 100,000 miles, the check engine light came on and showed error codes P0171 and P0174, engine running too lean.
At that time, I changed the O2 sensors, spark plugs/wires, air filter, oil, fuel filter, and PCV. I also changed the DPFE sensor. The truck was ok for a while but the check engine light popped back on shortly after that. I have been so busy that I could not rent the scanner again and check the code until now.
The scanner still shows a code of P0171, bank 1 running too lean. I assume Bank 1 is the driver side. Looking at the O2 sensor data, the #1 sensors for both banks appear normal, meaning they fluctuate between lean and rich. The bank 1 #2 sensor which I assume is the sensor farthest from the engine on the drivers side is reading a constant rich at idle (volts about 0.6 to 0.7) Bank 2 #2 is reading constant lean (volts about 0.2) at idle.
When I changed the plugs, I noticed one plug on the drivers side had what appeared to be a buildup of sand/dirt around it. I could not change it and figured I would do it later. I have not changed it yet. I realize that was a mistake, but I figured 7/8 was better than 0/8 and I was leaving for vacation the next day. Maybe that plug is not burning all the fuel causing the one cylinder to send unburned gas through to the exhaust?
Does anyone have any thoughts on what might be causing this light to stay on with code P0171? Maybe I just need to have that plug changed?
Any and all help is appreciated. Thanks!
Andrew Lewandowski
Senior Member
Joined: Apr 2001
Posts: 1,678
Likes: 0
From: Northern Kentucky
That is sort of wierd and puzzling. This is just my opinion but it's a thought.
If that one plug was not burning fully ( ie: misfire) I would think it would throw a code P0301-P0308, 301 being cylinder 1 and 308 being cylinder 8. These trucks and their computers will detect a misfire. If it was a misfire though I think you should feel it and know. Mine has had a misfire twice now. The first time all of a sudden and this time I had a surging/bucking/hesitation feeling for 3 days before I got a MIL.
It's also possible that you got a bad O2 from the parts place. See if you can't defective exchange that one or pair. At least then there is no possibility left it is in the O2's.
From there on, I am sorry but I am out of clues.
If that one plug was not burning fully ( ie: misfire) I would think it would throw a code P0301-P0308, 301 being cylinder 1 and 308 being cylinder 8. These trucks and their computers will detect a misfire. If it was a misfire though I think you should feel it and know. Mine has had a misfire twice now. The first time all of a sudden and this time I had a surging/bucking/hesitation feeling for 3 days before I got a MIL.
It's also possible that you got a bad O2 from the parts place. See if you can't defective exchange that one or pair. At least then there is no possibility left it is in the O2's.
From there on, I am sorry but I am out of clues.
Senior Member
Joined: Aug 2001
Posts: 246
Likes: 0
From: Monument, CO
when you get 171 and 174 together it's usually related to an intake manifold leak or a vaccuum leak of some sort, if you had any kind of work done on you truck make sure that all the parts they messed with are tight and that no bolts or nuts are missing, if you have access to a scanning tool, try checking the short and long fuel trims, if they go negative more than -10 or significantly more than you definately have a vaccuum leak or a intake manifold leak. good luck
