Fuel Trim % still pegged

[MrZumma]

I have just installed 2 new O2 sensors and the Fuel Trim % for the B1S2 sensor is still pegged at 99.06%. It never moves from there irregardless of throttle position, engine load, coolant temp., etc.. As a test, with the engine off, I can turn the ignition to 'ON' and it will still read 99.06% while B1S1 Fuel Trim % reads 0. I have unplugged the suspect sensor and I still get the same 99.06% reading. I am at a loss, other than a malfunctioning computer, as to what the problem could be.

Thanks for any insight here..

 

[Koffer]

I have just installed 2 new O2 sensors and the Fuel Trim % for the B1S2 sensor is still pegged at 99.06%. It never moves from there irregardless of throttle position, engine load, coolant temp., etc.. As a test, with the engine off, I can turn the ignition to 'ON' and it will still read 99.06% while B1S1 Fuel Trim % reads 0. I have unplugged the suspect sensor and I still get the same 99.06% reading. I am at a loss, other than a malfunctioning computer, as to what the problem could be.

Thanks for any insight here..

I would check for any wires that maybe pinched or rubbed through.
If you dont find anything (trans. area, egr pipe and other known rub points ) then go to the computer and check where the wires comeout of the ECM and rub on the dash bracket.
If everythings up to par pull just those wires out of the ECM plug and run a code check again.
If still there then its a ECM problem if not showing anymore then its a wireing problem . HTH some

 

[CJF]

Are the sensors OEM?

 

[MrZumma]

Are the sensors OEM?

Absolutly. Purchased from Dan...

 

[MrZumma]

I would check for any wires that maybe pinched or rubbed through.
If you dont find anything (trans. area, egr pipe and other known rub points ) then go to the computer and check where the wires comeout of the ECM and rub on the dash bracket.
If everythings up to par pull just those wires out of the ECM plug and run a code check again.
If still there then its a ECM problem if not showing anymore then its a wireing problem . HTH some

I'll give that a shot. Much appreciated...

 

[SUMOTOY]

I would check for any wires that maybe pinched or rubbed through.
If you dont find anything (trans. area, egr pipe and other known rub points ) then go to the computer and check where the wires comeout of the ECM and rub on the dash bracket.
If everythings up to par pull just those wires out of the ECM plug and run a code check again.
If still there then its a ECM problem if not showing anymore then its a wireing problem . HTH some

I believe the diagnostic plug has a 02 voltage output read. Use a no load meter, you should see .4=.5v off it (with fluctuations). Sounds like a ground problem in the signal wiring from the 02 to the ECU. Otherwise you should have a 02 sensor heater code malfunction code popping up as well.

HTH

ST

 

[hobbes]

Silly question, but is it not supposed to be like that? My motor, I believe, has the same value. I have no codes (except a pending PO401) and it runs fine. My O2 graphs look reasonable (having nothing to compare it to). I believe I still have the original O2 senors in.

I could have the wrong sensor since this is off the top of my head. I remember seeing it and it looking funny, however. I just assumed it was normal since nothing was flagged. I'll look this weekend when I get back home.

 

[hobbes]

Zumma, where do you stand on this? I just hooked up my scan tool. I confirmed my B1S2 fuel trim is a steady 99.06%.

My idling voltage on the B1S1 oxygen senor is in the correct range (.1 -.9). I did not confirm my B1S2 output at 30mph, but the graph "seems" okay.

I didn't see anything in the book that pointed to B2 fuel trim numbers. I have suspect this is normal.

 

[scottm]

I've posted some graphs of my O2 sensor readings before, after installing aftermarkets, and after installing sensors from cDan. Hope this helps.

https://forum.ih8mud.com/showthread.php?t=75975

https://forum.ih8mud.com/showthread.php?t=89849

 

[MrZumma]

Zumma, where do you stand on this? I just hooked up my scan tool. I confirmed my B1S2 fuel trim is a steady 99.06%.

My idling voltage on the B1S1 oxygen senor is in the correct range (.1 -.9). I did not confirm my B1S2 output at 30mph, but the graph "seems" okay.

I didn't see anything in the book that pointed to B2 fuel trim numbers. I have suspect this is normal.

I didn't have a chance to do too much troubleshooting this weekend. When I was replacing the rear O2 sensor last weekend, I snapped off one of the studs. So I spent this weekend extracting that stud and cleaning the threads in the flange.

I did do an examiniation of the wire harness from the rear O2 sensor to the ECM and nothing caught my eye in terms of worn or broken insulation. I did check much closer where the harness passes through the firewall and near the dash bracket, but all looked fine. I will pull the pin from the ECM next weekend and get the readings then.

 

[MrZumma]

I've posted some graphs of my O2 sensor readings before, after installing aftermarkets, and after installing sensors from cDan. Hope this helps.

https://forum.ih8mud.com/showthread.php?t=75975

https://forum.ih8mud.com/showthread.php?t=89849

Thanks for posting links to those discussions. My STFT and LTFT react like those in the graph after you installed OEM and after I replaced both O2 sensors. If you are thinking about it the next time your OBDII scan tool is plugged into the cruiser, it would be interesting to see if your FT Percentage (different than the STFT/LTFT) on B1S2 is pegged at 99.06% as well.

Thanks again

 

[scottm]

I had to reset P0116 today, and ran the chart on the four fuel trim readouts available. I can only get short- and long-term fuel trim, not seeing anything else. Is there something else I'm not getting access to?