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Ok I will have to pull them again to give you the numbers, but here is the explaintion. O2 sensor bank 2 sensor 2 replced and it comes back with a day.....the same if I had just cleared the code with my reader. I also get bank 1 lean and bank 2 lean. The car is pretty gutless compared to my SHO and it has a huge spark knock problem in the summer if you try to accelerate slowly from any speed.....will pull the code tomorrow if I remember. Any help would be great so I can get rid of my check engine light......I have a Mac tools scanner that I do all my reading with. Thanks in advance
 

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Discussion Starter #2
Help

Ok here is the info from my reader...4 codes

PO156 - O2 Sensor Circuit Malfunction, Bank 2, Sensor 2

PO161 - O2 Sensor Heater Circuit - Curcuit Malfunction, Bank 2, Sensor 2

PO171 - System too Lean (Bank 1)

PO174 - System too Lean (Bank2)

Readings recorded when PO156 is tripped

PO156 Freeze Frame
-Fuel Sys Stat B1
OL, Drive Cond

-Fuel Sys Stat B2
O

-Calculated Load
45.88%

-Coolant Temp
92 C

-ST Fuel Trim B1 - 0.00%
-LT Fuel Trim B1 - 17.17%
-ST Fuel Trim B2 - -13.28%
-LT Fuel Trim B2 - -17.95%

-Engine Speed - 1604.25 RPM
- Vehicle Speed - 58 km/h

Any help would be great.......
 

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Your left rear oxygen sensor is most likely bad. Replacing it should knock out P0156 and P0161. The other 2 codes are most likely caused by either a dirty/faulty MAF sensor or a vacuum leak. Other possibilities include a weak fuel pump, faulty fuel pressure regulator, or clogged fuel filter. First clean the MAF sensor, make sure there aren't any vacuum leaks, and then reset the computer.
 

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Discussion Starter #4
help

I have cleaned the MAF, the passenger lower O2 I replaced as well.......the code come back.....I have also check the intake and vacuum leaks and didn't seem to have any. I cleared the codes today, no light right now but if you scan it while it is runningwith no CEL then you still get the 2 O2 sensor codes. Think it may be a wiring issue?
 

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help

Opps..........well I will switch that one out then.......Thanks
I was told by a friend that bank 2 was the passenger side...Thanks for the heads up.
 

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not only do you have your banks confused, but also as master486 said, its the wrong one because the rear one (after the catalytic converter) is not the one that the computer uses to fine-tune the air-fuel mixture...its the upper one before the cat

also, you need to check your fuel pressure with the vacuum line off the regulator (and plugging up the vacuum line of course so you dont make a vacuum leak :))...you should get 39 PSI
 

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PO171 - System too Lean (Bank 1)
PO174 - System too Lean (Bank2)

...
...

-ST Fuel Trim B1 - 0.00%
-LT Fuel Trim B1 - 17.17%
-ST Fuel Trim B2 - -13.28%
-LT Fuel Trim B2 - -17.95%
Why is there a code for both banks being lean, when the LTFT on bank 2 is adjusting for a rich condition?

not only do you have your banks confused, but also as master486 said, its the wrong one because the rear one (after the catalytic converter) is not the one that the computer uses to fine-tune the air-fuel mixture...its the upper one before the cat
Bank 2 Sensor 2 is the rear driver side sensor, and it does not affect the fuel trim. Clean the MAF sensor just for the hell of it and see if that helps.
 

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When I bought my 95 4.6L about five years ago, it was getting the P0171 and P0174 codes intermittently and then constant after a few months. There is a rubber T-connector on the vaccum that connects to the back of the intake manifold on the passenger side. Apparently the T-connector is notorious for developing pin hole leaks. I sealed with an inner tube patch.
 

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When I bought my 95 4.6L about five years ago, it was getting the P0171 and P0174 codes intermittently and then constant after a few months. There is a rubber T-connector on the vaccum that connects to the back of the intake manifold on the passenger side. Apparently the T-connector is notorious for developing pin hole leaks. I sealed with an inner tube patch.
The rubber T you are talking about is only on the 94/95 4.6L cars.
 
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