Code P0171 "O2 sensor?"
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Senior Member
Joined: Dec 2009
Posts: 120
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Code P0171 "O2 sensor?"
Just bought a used 2003 XLT V6 with 87,000 miles
"Service engine soon" light came on with the code P0171 - Bank one lean
Printout from Autozone
Definition
Fuel trim bank one condition
Explanation
The powertrain control module uses the oxygen sensor to calculate the air/fuel ratio of the engine. The computer has recognized a rich or lean condition on one engine bank only.
Probable cause
1. If bank one and two codes set together suspect fuel pressure or MAF (Mass Air Flow) sensor.
2. Oxygen sensor defective.
3. Ignition misfire-repair
4. Fuel injector problem.
The truck seems to be running smooth with no rough idle or hesitation. My gas mileage has worsend.
Correct me if I am wrong.
can't be #1 because only bank one is registering.
Can't be #3 becuase a misfire would cause rough idle / running of engine
Will #4 cause the engine to exibit something physically? if so what?
I am thinking it is the O2 sensor.
"Service engine soon" light came on with the code P0171 - Bank one lean
Printout from Autozone
Definition
Fuel trim bank one condition
Explanation
The powertrain control module uses the oxygen sensor to calculate the air/fuel ratio of the engine. The computer has recognized a rich or lean condition on one engine bank only.
Probable cause
1. If bank one and two codes set together suspect fuel pressure or MAF (Mass Air Flow) sensor.
2. Oxygen sensor defective.
3. Ignition misfire-repair
4. Fuel injector problem.
The truck seems to be running smooth with no rough idle or hesitation. My gas mileage has worsend.
Correct me if I am wrong.
can't be #1 because only bank one is registering.
Can't be #3 becuase a misfire would cause rough idle / running of engine
Will #4 cause the engine to exibit something physically? if so what?
I am thinking it is the O2 sensor.
Last edited by ddbrown; Jan 28, 2010 at 06:20 PM.
99 F150 Blue x-cab 4x4
Joined: Feb 2010
Posts: 14
Likes: 0
From: Glen Burnie, MD
Same exact thing happen to me last night everything the same. I reset the computer and it hasnt come back. But ii to am looking for information on exact location of the 02 sensor and if anyone has changed theres how hard it was to change and all. If you find anything out please let me know and ill do the same.
Thread Starter
Senior Member
Joined: Dec 2009
Posts: 120
Likes: 3
Bank 1(one) is the side of the #1 cylinder which is the passenger side on the V6.
Two weeks ago I replaced the "upstream" sensor which is the one before the catalytic converter close to the exaust header.
It was releatively easy to access with the truck on a lift.
When I turned the front wheels all the way to the left; I could see the sensor with the wheels/exaust headers at eye level.
I have driven about 325 miles (2 weeks) and so far it has not came back.
My gas mileage has improved, so I think it was it.
Two weeks ago I replaced the "upstream" sensor which is the one before the catalytic converter close to the exaust header.
It was releatively easy to access with the truck on a lift.
When I turned the front wheels all the way to the left; I could see the sensor with the wheels/exaust headers at eye level.
I have driven about 325 miles (2 weeks) and so far it has not came back.
My gas mileage has improved, so I think it was it.
99 F150 Blue x-cab 4x4
Joined: Feb 2010
Posts: 14
Likes: 0
From: Glen Burnie, MD
Don't know if I want to post this or not but I fixed my 02 sensor code issue. I bought two sensors for bank 2 on my code I posted earlier. While changing my oil yesterday I looked over my engine like I do every time and what to my surprise my MAF sensor fell out of my intake. I reset my computer and two days now n a few 100 miles later tada no more light. I'm suck an idiot!