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HuskerFlex

checking O2 sensors?

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is there a way to test if an O2 sensor is working?  I have a feeling that this may be why I've been driving on a perpetual CEL (lean burn bank 1) for the last 3 months or so... regardless of how rich I set the conversion kit on my Lumina.

 

I fear taking the old lady (Lucy the Lumina ::)) into a service station, as I've already had one yahoo tell me "I know what your problem is... it's that damn kit, your trying to make the car burn something it wasn't made for"... ???

 

Haven't gone back there!

 

I was just wondering how I could have the O2 sensors checked to see if this was the "easy fix" I need

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I can check mine with my OBD-II computer (Ultra-Gauge). Maybe places like AutoZone or AdvanceAuto can give you a readout?

 

Of course, you have to have the values from the manufacturers first to see if the sensor operate withing their range.

 

I had one reported to operate out of range here and there, one of the ones at the bottom of the vehicle, yes, the ones exposed to everything out there.

 

I took the sensor out, cleaned the whole thing (exhaust and sensor) with a cupper brush, applied conduction grease on treads, electric parts cleaner on the, well electric parts, and put everything together.

 

Today, after almost 1 year, still operating in their range.

 

Greetings!

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I do not know the official test method but if you have a scan tool with live readout (and data capture is nice for download to pc) you can watch your O2's do their oscillations. A narrow band 02 should fly (fast) each side 0.4 v from about 0.15 to 0.85 (more common .2 to .83). The .8 is rich, the .2 is lean, and the .4 is about stoich. If one sensor on the front banks (O 1.1 or O 2.1) is moving slower than the other or not ranging as far then it may be worth digging in deeper to see if the lazy one is defective. Do not get distracted by the rear O2 - it will likely move slower- it is monitoring the cat converter.

 

A number of decent scan tools can be had on sale (internet) for around the $120 range that can do this. You do not need the $6000 shop version for such basic view.

 

Perhaps Corey or someone more into this can answer better then I for the official test method.

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Some good info already posted.  Though, I would first caution that unless you are re-setting the CEL each time, you may simply be seeing the light due to a stored code. A momentary lean code could make the light stay on for weeks or more, even though the event which set it only lasted for a few seconds.  IIRC, there has to be a fairly large number of start/drive cycles with no codes to finally get the light to turn off (at least on vehicles I am familiar with

).

 

Second - is this a V6? if you have two banks, the simplest thing would be to swap sensors between the two banks.  If the lean code follows the sensor, then it's most likely a bad sensor.  If it stays on the same bank, it could be an actual issue with the fueling, or a problem with the wiring/ECU on that side.

 

If it's a 4 cyl with only one bank, A scan gauge would certainly tell you what the sensor is reading, but I don't think it will tell you if the reading is actually correct.  The only way to do that is to physically test the sensor.  Cheapest/easiest way would be to pull the sensor out of the exhaust, but keep it plugged in to the electrical harness and turn the ignition to 'on'.  This should turn on the O2 sensor heater and in ~10 seconds the scan gauge should show a reading of full lean (ie pegged at 28-32 AFR)  If you then take a rag with a bit of E85, gas, carb cleaner, etc on it (and I do mean a bit, all you need is some vapor) Wrap the rag around the sensor and the scan gauge should go full rich and stay there.  If it doesn't go rich, or goes rich then backs off in a few seconds, there is a problem somewhere.  Most likely the sensor is bad, though a thorough check would be to check for continuity on the wires between the ECU and O2 sensor and also check for grounds and proper voltages on the wires.

 

Standard precautions apply...flammable substance, rag, electricity, etc.

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Second - is this a V6? if you have two banks, the simplest thing would be to swap sensors between the two banks.  If the lean code follows the sensor, then it's most likely a bad sensor.  If it stays on the same bank, it could be an actual issue with the fueling, or a problem with the wiring/ECU on that side.

 

 

yup... v6 Chevy 3.1...  it is always "lean burn bank 1"... so this makes perfect sense... if I swap them, and get a "lean burn bank 2"... then it is THAT sensor that is the issue... if it continues to say "bank 1"... then there really is an issue there...

 

I'll have to look into this!  Is swapping these "do-hickeys" something the "average suburban dad with a ratchet wrench and a pair of pliers can take on? ::)

 

You folks on here really do rock by the way... so much knowledge and real world experiences, and a wiliness to help!  Thanks!

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It should be fairly easy.  I don't think a ratchet/socket will fit over the  sensor due to the wires.  But a plain wrench, or even a line wrench should do the trick.  You might be able to borrow a true O2 sensor wrench from the local auto parts store if the sensor is a real pain.

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All of the biggie parts stores have a 'loan-a-tool' service. Where you put down a deposit, borrow a tool, use it and return it, get your money back.

 

Just avoid cheap electrical parts like Wells(what Autozone sells).

 

 

There are tests for the sensors.  If you register on the Autozone site, they have vehicle specific sensor tests on there.

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How many miles on these o2's? If it's close to 100k you might as well replace the front ones. On older vehicles, the rear just reports the health of the cat.

 

You can find special notched sockets on fleeBay to remove them (since the wire comes out the end), o/w like what was said, you'll have to use a wrench. You'd also want a thin film of ant-iseize on them, careful of where you put it tho.

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Yes, you most likely will need a plain wrench, many of these sensor are located in such convenient spots which make the use of usefull tools useless.

 

When I changed the one on wife's car on 1 side (cause it was out of range), I did the other side as well, even though it was still within acceptable range. The sensor was around $30, I figured better be safe than sorry.

 

Greetings!

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