Can someone please help by posting the values (voltage readings) of all the oxygen sensors (4) of a 2001 QX4 and indicate what they meant. 1=rich(?) 0=lean(?) and perhaps 0.5=ok(?)
Thanks for help
Oxygen sensor values
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computerdna
- Posts: 21
- Joined: Sun Dec 07, 2003 1:42 pm
- Car: QX4
Oxygen sensor values
Deal all,
Can someone please help by posting the values (voltage readings) of all the oxygen sensors (4) of a 2001 QX4 and indicate what they meant. 1=rich(?) 0=lean(?) and perhaps 0.5=ok(?)
Thanks for help
Can someone please help by posting the values (voltage readings) of all the oxygen sensors (4) of a 2001 QX4 and indicate what they meant. 1=rich(?) 0=lean(?) and perhaps 0.5=ok(?)
Thanks for help
the voltages of all 4 will vary between 1v and 0v "raised is rich low is lean" the front 2 sensors should sweep from rich to lean like 5 times in 10 seconds. the rears should be more steady and where they are doesnt really matter as long as they are not sweeping within 75% of the front o2 sweeps at a steady 2000 rpms.
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computerdna
- Posts: 21
- Joined: Sun Dec 07, 2003 1:42 pm
- Car: QX4
it is always measured XX parts air to 1 part fuel. so if your obdII scanner says 15 the 1 part fuel is assumed.
also the rear O2's have no effect on fuel control or ratio they are there simply to moniter cat effeciency. the only time they would ever be used for fuel control is if the fronts went completely dead. the result would be a very poorly running vehicle since it would be in a fail safe state and the cat is cleaning up a large portion of what is burnt the rear O2's would be very confused on what the vehicle was actually doing.
also the rear O2's have no effect on fuel control or ratio they are there simply to moniter cat effeciency. the only time they would ever be used for fuel control is if the fronts went completely dead. the result would be a very poorly running vehicle since it would be in a fail safe state and the cat is cleaning up a large portion of what is burnt the rear O2's would be very confused on what the vehicle was actually doing.
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computerdna
- Posts: 21
- Joined: Sun Dec 07, 2003 1:42 pm
- Car: QX4
My OBDII scanner doesn't have the Air:Fuel ratio
After I fixed the misfire problem, I still have the ¡°cat efficiency low bank #1¡± DTC. If in fact the cat is dead, shouldn't I be smelling gas from the exhaust? I am still trying to find out whether it is the oxygen sensors or the cat. Please give some tips on how to diagnose this problem. I have only one DTC and that's ¡°cat efficiency low bank #1¡±
When I was still having the misfire problem in cylinder #1, my bank 1 oxygen sensor #1 will always report a LEAN condition to the ECM and telling it to add more fuel, thus my car was always running RICH. Since I have just fixed the misfire problem, my question is How long will it take the ECM to control the Fuel Trim back to normal? Will it be an instant adjustment or will it take a few driving cycles?
Thanks and sorry to have so many questions. A newbie here to learn :thinker
After I fixed the misfire problem, I still have the ¡°cat efficiency low bank #1¡± DTC. If in fact the cat is dead, shouldn't I be smelling gas from the exhaust? I am still trying to find out whether it is the oxygen sensors or the cat. Please give some tips on how to diagnose this problem. I have only one DTC and that's ¡°cat efficiency low bank #1¡±
When I was still having the misfire problem in cylinder #1, my bank 1 oxygen sensor #1 will always report a LEAN condition to the ECM and telling it to add more fuel, thus my car was always running RICH. Since I have just fixed the misfire problem, my question is How long will it take the ECM to control the Fuel Trim back to normal? Will it be an instant adjustment or will it take a few driving cycles?
Thanks and sorry to have so many questions. A newbie here to learn :thinker
when your cyl was missfiring how often did you drive it with the cel on and flashing? more then 20 mins?? you most likely destroyed the cat. When the check engine light flashes that is a warning that cat failure is eminate if you continue to drive it.
the 2 leading causes of cat failure are#1 lean condition(misfire)#2 rich condition (leaking injectors,out of spec[bias]O2 sensor,airflow meter out of spec)
I suspect the code your getting is accurate and your cat is done. I know your OBDII scanner does not have graphing capability but if you had a way to graph both the front and rear o2 sensor for that bank at the same time you could watch the sweeps of both O2's and see if they are equal that would indicate the cat is truly dead. With the factory scan tool [ConsultII] you can bring both up at the same time and get a true site as to what is going on. Typically if the cat is bad both readings will mirror each other
the 2 leading causes of cat failure are#1 lean condition(misfire)#2 rich condition (leaking injectors,out of spec[bias]O2 sensor,airflow meter out of spec)
I suspect the code your getting is accurate and your cat is done. I know your OBDII scanner does not have graphing capability but if you had a way to graph both the front and rear o2 sensor for that bank at the same time you could watch the sweeps of both O2's and see if they are equal that would indicate the cat is truly dead. With the factory scan tool [ConsultII] you can bring both up at the same time and get a true site as to what is going on. Typically if the cat is bad both readings will mirror each other
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computerdna
- Posts: 21
- Joined: Sun Dec 07, 2003 1:42 pm
- Car: QX4
I drove to a shopping mall and back today (141.5 miles, all highway), and I got 19.25 mpg. I was going at average of 65-70 mph the whole trip and was surprised by the result. The manufacture's spec was 15/19. Since I am all the way above the 19 mark, can I be safely assumed that the oxygen sensor #1 of bank 1 is working properly? If this assumption is correct, then there are only two things left ¨C the rear sensor or the cat.
Back to the misfire, when it occurs, the engine light only blinks for about 30 seconds then turn back to steady. Engine light only blinks when I accelerate and sometimes blinks at steady highway speed. I have never gone above the 45 mph mark when the engine light blinks and it never blinks for more than 30 to 40 seconds at a time.
The longest trip that I have driven with a misfire was about 30mins (had to get home), but the engine light blinks no longer than 40 seconds at a time, then pauses for a min or so, then blinks again.
Can the oxygen sensors be switched between bank 1 and bank 2? The cat is expensive, I just wanted to make sure before I go ahead to replace it. shouldn't I be smelling gas if the cat is dead?
Thanks.
Back to the misfire, when it occurs, the engine light only blinks for about 30 seconds then turn back to steady. Engine light only blinks when I accelerate and sometimes blinks at steady highway speed. I have never gone above the 45 mph mark when the engine light blinks and it never blinks for more than 30 to 40 seconds at a time.
The longest trip that I have driven with a misfire was about 30mins (had to get home), but the engine light blinks no longer than 40 seconds at a time, then pauses for a min or so, then blinks again.
Can the oxygen sensors be switched between bank 1 and bank 2? The cat is expensive, I just wanted to make sure before I go ahead to replace it. shouldn't I be smelling gas if the cat is dead?
Thanks.
that gas milage is good and does indicate HO2B1S1 is ok. No you will not smell fuel if the engine is running at its most effecient level the fuel is being burnt in the combustion chamber there for the HC content is lower. Do as I said take it to a dealer have them hook up consultII tell them to pull up both O2's for bank 1 in line graph mode and moniter it while driving at a steady speed above 30 mph. Tell them you would like to ride with them and watch the consult. if both graphs are doing exactly the same thing at a steady speed it indicates a bad cat. after you see that have them pull up both O2's for bank 2 and watch those you should see something drastically different. the front O2 should be sweeping much like the one was on the other bank but the 2nd sensor should be much different almost steady. note on accel and decel the second o2 will mirror the front o2 but that is normal. It is at steady speeds you need to watch them.This will give you some assurance on what is going on.