B2S2 Fuel Trim Error
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B2S2 Fuel Trim Error
Hi everyone, I'm new to the forum and have a question about a O2 sensor error. I am an amateur mechanic who does pretty good with classic cars (I'm restoring a 73 Mustang) but am just diving into working on my newer stuff. So I'm pretty dangerous there. 
I have a friend who just purchased a 2005 Expedition with the 5.4 engine. Awhile back I bought an Auto Enginuity scan tool/software. We ran a scan and found that the "B2S2 O2 Fuel Trim %" reading was consistently putting out a reading of 99.06. I'm not sure what the "B2S2 O2 Fuel Trim %" reading refers to, as opposed to O2 voltage, which is a separate reading. Does it mean that the bank 2 rear O2 sensor is bad? Or the air/fuel ratio is wrong for bank 2? Or is there something else wrong?
Thanks
I have a friend who just purchased a 2005 Expedition with the 5.4 engine. Awhile back I bought an Auto Enginuity scan tool/software. We ran a scan and found that the "B2S2 O2 Fuel Trim %" reading was consistently putting out a reading of 99.06. I'm not sure what the "B2S2 O2 Fuel Trim %" reading refers to, as opposed to O2 voltage, which is a separate reading. Does it mean that the bank 2 rear O2 sensor is bad? Or the air/fuel ratio is wrong for bank 2? Or is there something else wrong?
Thanks
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Thanks Alloro. Any way to tell if it's the sensor or the cat? Or do you just replace the sensor first cause it's cheaper and see if the problem goes away? If we need to replace the cat, is it best to do both at the same time?
Hotshot
Joined: Jan 2004
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From: St Louis
More likely it's a problem with the scanner or software since the PCM cannot command trims that high. Besides, the downstream sensors don't have anything to do with the fuel trims.
Did you run the scan out of curiosity or was the MIL on? If the MIL was on, what was the DTC and the freeze-frame data? If it was just curiosity, well, you've heard about the cat.
Did you run the scan out of curiosity or was the MIL on? If the MIL was on, what was the DTC and the freeze-frame data? If it was just curiosity, well, you've heard about the cat.
Fleet Owner
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From: 0,0,1
You could swap the rear O2 sensors for banks 1 and 2 to see if the problem follows the sensor or not. If it does follow the sensor then change the sensor, if it doesn't then check the sensor wiring or change the cat.
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I don't think it's a scanner/software problem, I've used this on several of my and my friend's cars and it's always been accurate. Plus all of the other readings seem to be functioning.
Originally when he got the truck, there was no MIL. It was idling a little rough and it has about 100K on it so we decided to give it a shot of Seafoam. After we ran it through, the MIL came on. When I brought up the code on the laptop I accidentally hit the Clear Codes button while I was shifting the laptop around to try to see the screen. Dumb, I know, but I can hardly see that screen when it's sunny out. No problem, I figured, we'll just drive it around a bit and it'll come back on. But it never did. Just the bad fuel trim reading So I don't know what the code was.
I'll try the sensor swap to start with and see what that does. Thanks guys.
Originally when he got the truck, there was no MIL. It was idling a little rough and it has about 100K on it so we decided to give it a shot of Seafoam. After we ran it through, the MIL came on. When I brought up the code on the laptop I accidentally hit the Clear Codes button while I was shifting the laptop around to try to see the screen. Dumb, I know, but I can hardly see that screen when it's sunny out. No problem, I figured, we'll just drive it around a bit and it'll come back on. But it never did. Just the bad fuel trim reading So I don't know what the code was.
I'll try the sensor swap to start with and see what that does. Thanks guys.
Last edited by DWinTX; Jan 23, 2011 at 06:01 PM. Reason: sp
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