Codes galore

[crazycarl]

So I may have let a small issue become slightly bigger, and now I'd like to get input from you experts on here.

Long story short, truck ran decent up north but pumped full of ethanol for its 80k mile life. Brought it down south, it hasn't seen ethanol since, and one of the first things I did was running some Seafoam through the intake. After that I threw my first engine code for a bad o2 sensor. I let it go because truck still ran fine and I was curious if it really was the o2 sensor or IAC (gathered that from some reading online)

Next, changed my intake gasket as it had a pretty decent leak. First start-up truck ran smooth as ever. Thought the problem was solved until about ~100 miles later SES light came back on, same code for o2 sensor. Side note: After changing out that intake gasket, I still notice a little coolant disappearing. (90% sure its not the radiator)

I plan on testing it to make sure it isn't the head gasket. Could I have clogged the cat? Are the sensors bad from the Seafoam? Or if it is indeed a head gasket, could the coolant make it to the exhaust and foul the sensors?

Codes being thrown:
p0137
p0138
p1040

I know the first two are bank one up-stream. Not sure about the third...

After typing this I've convinced myself it could be the catalytic converter now.... Any thoughts/input are appreciated!

[HenryJ]

My cat never set a code and it was badd , bad. Pressure test for a coolant leak and start replacing bad sensors would be my best guess. How many miles on your O2 sensors? If you have 100k miles, you are due for a new set.

[crazycarl]

I believe they are original. Truck has almost 90k miles on it now.

[HenryJ]

You have cleared them and they did return, right?

Seeing as this is bank 1 sensor 2 reading, low, high and not at all...I'd say it is probably bad or the wiring is damaged. Check the connector and make sure the pins are intact.
Sensor 2 does not influence the engine functions like the bank 1 sensor 1 and bank 2 sensor 1 do. It monitors the converter efficiency. The problem is that they all seem to go out about the same time. Replacing them all is an expensive pill to swallow, but a good investment. Fuel metering will be improved with accurate sensors.
I bought mine from Rockauto.com . Buy the OEM AC Delco sensors and don't cheap out on the cut-rate sensors. I have not had good luck with those.
Use the discount code we keep going in the classifieds, or google a current one. That will save the cost of shipping usually.

[crazycarl]

As far as clearing, I had the batter disconnected. That clears them correct?

And upon further investigating. Those codes all have to do with the same sensor, bank 1 sensor 2. If the website I was looking at was correct....

(http://www.obd-codes.com)

[killian96ss]

The factory O2 sensors start losing efficiency by 70k miles and are pretty much done by 100k so it sounds like yours should be replaced. The 2 pre cat sensors should be replaced first since they are used by the PCM to maintain the proper a/f ratio and keep emissions low. If you have enough $, replace all 3 sensors, but if you can't just buy 2 and reuse one of the old ones for the post cat sensor which is just there to verify that the cat is working properly. Make sure you buy AC Delco sensors! A lot of the aftermarket O2 sensors can cause mild problems like surging, and loss of fuel economy. Rock Auto usually has pretty good prices compared to the local parts stores and you can get an additional 5% off with a coupon code.

Steve

[crazycarl]

Shoot. I bought a Denso to replace it...

But I'll get them replaced again if need be. This thread has me feeling better. Thanks for the direction guys

[killian96ss]

You should be fine with the Denso sensors. They are good quality, not to mention a GM supplier like AC Delco and Delphi. Stay away from Bosch O2 sensors and spark plugs! They are known to cause problems in GM vehicles.

Steve