Oxygen Sensor ?

[hagglerock]

I have a 2002 Suburban with a 5.3 Flex Fuel, 90K miles. Getting a Bank 1 to lean code on the OBDII. I am guesing it is a oxygen sensor issue. This model uses 4 oxygen sensors, 1 before and 1 after each catylitic converter. Luckaly they are all the same p/n, unluckely they are about $90 each! Any advice on which sensor, before or after c/c, is more likely to fail .

Any help is greatly appreciated

[Scrapper]

are you getting these 0-2's from dealer or a parts store? thats awfull high for 0'2's. did you have coils checked?

[hagglerock]

These were Bosch OE styles (p/n 13193) from Autozone. The coil packs can cause this ?

[j cAT]

Originally Posted by hagglerock

I have a 2002 Suburban with a 5.3 Flex Fuel, 90K miles. Getting a Bank 1 to lean code on the OBDII. I am guesing it is a oxygen sensor issue. This model uses 4 oxygen sensors, 1 before and 1 after each catylitic converter. Luckaly they are all the same p/n, unluckely they are about $90 each! Any advice on which sensor, before or after c/c, is more likely to fail .

Any help is greatly appreciated

lean code may mean low fuel pressure or vacuum leak like intake manifold gaskets...or other leaks...90,ooomi is low for failure of O2 ..the upsteam O2 sensors are the controlling sensors ,,, the down stream sensors report cat efectiveness..

check fuel pressure and intake for proper operation....

[hagglerock]

Another fact that I failed to add. This only happens when it gets below about 20 degrees F. It will idle very rough until it warms up then runs fine. The SES light will go out on it own after the outside temp stays above about 40 degrees F for a day or better.
Sorry for not adding that earlier

[Schrade]

Originally Posted by hagglerock

Another fact that I failed to add. This only happens when it gets below about 20 degrees F. It will idle very rough until it warms up then runs fine. The SES light will go out on it own after the outside temp stays above about 40 degrees F for a day or better.
Sorry for not adding that earlier

Light goin' out means nothing - the code and the problem is still there. It will store as Hxxxx history. Some other types of codes can stop lighting up, after a problem is fixed, and several drives cycles are done with no occurrences. I think they're NOT engine/PCM codes tho'.

Before spending $90, swap the front and rear for the faulty side. Some GM vehicles have no separate fault indication for the rear O2.

[j cAT]

Originally Posted by hagglerock

Another fact that I failed to add. This only happens when it gets below about 20 degrees F. It will idle very rough until it warms up then runs fine. The SES light will go out on it own after the outside temp stays above about 40 degrees F for a day or better.
Sorry for not adding that earlier

I still would check out what I mentioned earlier...also because the O2 failure code comes and goes it could very well be the sensor...the upsteam sensors should be replaced at 100,ooomi...so this would be a little premature....

I have had this falure Lt come and go before and it was indeed the sensor...also you can remove both sensors and check wires and connections also swap locations ..see if the sensor code changes location...


remove sensor when the exhaust is hot ,,they should come out easier.

[JMFite]

I had the same issues with a 2003 silverado.

I changed both o2 sensors out in front of the cat's and the light went off for a couple of weeks then came back on. I just drove it until i had acceleration issues (about 3 months). It ended up being a clogged cat on the passenger side. Changed converters (its a one piece wye pipe) and all is well.

I also had problem with light coming on in cold weather only.

[hagglerock]

Update.

It ended up being a vacume leak at the intake manifold. Gasket set was about $40 and took about 3 hours to complete. Not very difficult, just had to locate a good quality in-lb. torque wrench to reassemble.
Thanks for all the previous input

[j cAT]

Originally Posted by hagglerock

Update.

It ended up being a vacume leak at the intake manifold. Gasket set was about $40 and took about 3 hours to complete. Not very difficult, just had to locate a good quality in-lb. torque wrench to reassemble.
Thanks for all the previous input

since this was the intake gasket make sure the coolant system is properly maintained and clean....thermostat replacement ...also..

if the engine runs hotter the gaskets get damaged...

good luck...