PCM code PO174
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Mountain Pass
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From: Lovelady
PCM code PO174
I have a 2002 Ford F-150 and yesturday my check engine light came on so I checked it to see what it was cause my truck hadn't been runnin any differently lately. Well i got the code PO174 which means the fuel systme for bank 2 was too lean. But then it goes on to say in paranthesis Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank. Does anyone know what could cause this problem? The computer gave me 5 different probable causes, they are 1. If bank one and two are set toghether suspect a fuel condition or MAF sensor fault. 2. Failed HO2S21. 3. Ignition misfire condition. 4. Fuel injector probelm. or 5.Engine mechanical condition. yeah i can figure out that is one of these but i thought one of the guys on here that know what they are doin and what they are talking about can tell me the most common problem or what the most likely probable cause is the most common. like I said my truck aint been runnin any different but i did have that god awful nosie common from under my hood it got quiter but it still hasnt stopped well i appreciate the help and thanks in advance
Lead Driver
Joined: Sep 2006
Posts: 7,907
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Bank 2 is your driver's side.
Since it is only one bank, the OX sensor might be faulty, and fueling those cylinders 5,6,7,8 rich and you might not notice a drivabilty problem from this but less fuel mileage.
Other possible causes are an air leak in one of those cylinders at the intake to head port gasket.
Since you don't feel a miss of any sort, the injectors, plugs and coils should be good.
Another posability is a cracked exhaust manifold/ head pipe or ? allowing air to enter which the Ox sensor detects as a lean condition.
Best
Since it is only one bank, the OX sensor might be faulty, and fueling those cylinders 5,6,7,8 rich and you might not notice a drivabilty problem from this but less fuel mileage.
Other possible causes are an air leak in one of those cylinders at the intake to head port gasket.
Since you don't feel a miss of any sort, the injectors, plugs and coils should be good.
Another posability is a cracked exhaust manifold/ head pipe or ? allowing air to enter which the Ox sensor detects as a lean condition.
Best
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Bank 2 is your driver's side.
Since it is only one bank, the OX sensor might be faulty, and fueling those cylinders 5,6,7,8 rich and you might not notice a drivabilty problem from this but less fuel mileage.
Other possible causes are an air leak in one of those cylinders at the intake to head port gasket.
Since you don't feel a miss of any sort, the injectors, plugs and coils should be good.
Another possability is a cracked exhaust manifold/ nut-bolt missing broke, head pipe or ? allowing air to enter, which the Ox sensor detects as a lean condition.
Best I can do to sort out what may be happening by logic.
Otherwise I don't knows nuttin.
Good luck.
Since it is only one bank, the OX sensor might be faulty, and fueling those cylinders 5,6,7,8 rich and you might not notice a drivabilty problem from this but less fuel mileage.
Other possible causes are an air leak in one of those cylinders at the intake to head port gasket.
Since you don't feel a miss of any sort, the injectors, plugs and coils should be good.
Another possability is a cracked exhaust manifold/ nut-bolt missing broke, head pipe or ? allowing air to enter, which the Ox sensor detects as a lean condition.
Best I can do to sort out what may be happening by logic.
Otherwise I don't knows nuttin.
Good luck.
Thread Starter
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Mountain Pass
Joined: Mar 2007
Posts: 214
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From: Lovelady
Originally Posted by Bluegrass 7
Bank 2 is your driver's side.
Since it is only one bank, the OX sensor might be faulty, and fueling those cylinders 5,6,7,8 rich and you might not notice a drivabilty problem from this but less fuel mileage.
Other possible causes are an air leak in one of those cylinders at the intake to head port gasket.
Since you don't feel a miss of any sort, the injectors, plugs and coils should be good.
Another possability is a cracked exhaust manifold/ nut-bolt missing broke, head pipe or ? allowing air to enter, which the Ox sensor detects as a lean condition.
Best I can do to sort out what may be happening by logic.
Otherwise I don't knows nuttin.
Good luck.
Since it is only one bank, the OX sensor might be faulty, and fueling those cylinders 5,6,7,8 rich and you might not notice a drivabilty problem from this but less fuel mileage.
Other possible causes are an air leak in one of those cylinders at the intake to head port gasket.
Since you don't feel a miss of any sort, the injectors, plugs and coils should be good.
Another possability is a cracked exhaust manifold/ nut-bolt missing broke, head pipe or ? allowing air to enter, which the Ox sensor detects as a lean condition.
Best I can do to sort out what may be happening by logic.
Otherwise I don't knows nuttin.
Good luck.
Hotshot
Joined: Jan 2004
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From: St Louis
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Mountain Pass
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From: Lovelady
I have the 4.2L V6. the other day when my light came on i was sitten still idlin. Well i reset the computer and it was fine well today it was sitten idlin again and it came back on so im not sure but that might have somethin to do with it. And thanks for help in advance again
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Hey BigRed... I went through the same issue with the codes however, I have the 5.4. After replacing the front two O2 sensors all was fine. A while later I had PO171 and PO174. Without getting into all of my issues, headaches and posts, it turned out it was the mass air flow meter. I had to replace mine and haven't had any problems or codes since. You may want to try and clean it if you haven't already. Hop this will help. If you want to, look up my last few posts. Good luck..
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Mountain Pass
Joined: Mar 2007
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From: Lovelady
thanks for the help every one i havent done anything to it yet but i just got back hoime i was couple for a couple days buyt i plan on cleanin it out this weekend and seein what it does and ill keep everyone posted on it and again thanks to everyone for everything
Lead Driver
Joined: Sep 2006
Posts: 7,907
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A way to look at the codes generated by the Ox sensors is, they see the sum total of a problem upstream with the overall air/fuel delivery.
What needs to be done is not blame the doctor (ox sensors) but the cause of the difficulty, the Ox sensors detect.
Excess air causes the Ox sensors to try to correct the condition within limits (as they are supposed to do) as set in the program, by adding fuel. This takes the fuel tables to their limit, setting an alert code saying "rich" when the actual fault is to much air. This results in a miss understanding of the code discription. But is the only fast practical way to alert the driver there is a fault present.
By the way, an exact oppisite fault is detected in the same way but as a lean code discription with it's matching P code numbers.
The rich/lean refers to the shift in the computer fuel tables only and not what exact condition is causing the shift. That, you have to find!
Hope this helps all who have a need to handle these issues.
What needs to be done is not blame the doctor (ox sensors) but the cause of the difficulty, the Ox sensors detect.
Excess air causes the Ox sensors to try to correct the condition within limits (as they are supposed to do) as set in the program, by adding fuel. This takes the fuel tables to their limit, setting an alert code saying "rich" when the actual fault is to much air. This results in a miss understanding of the code discription. But is the only fast practical way to alert the driver there is a fault present.
By the way, an exact oppisite fault is detected in the same way but as a lean code discription with it's matching P code numbers.
The rich/lean refers to the shift in the computer fuel tables only and not what exact condition is causing the shift. That, you have to find!
Hope this helps all who have a need to handle these issues.
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