Bad O2 Sensors????

bojohnson2 · February 14, 2007

If the O2 sensors are bad what symptoms are present? Is it possible to have bad O2 sensors and not have the SES light on?

jason2006 · February 14, 2007

Yes , they can go bad and not trigger a CEL. The symptoms are gradual fuel economy loss.

If the O2 sensors are bad what symptoms are present? Is it possible to have bad O2 sensors and not have the SES light on?

Bish · February 14, 2007

Yes , they can go bad and not trigger a CEL. The symptoms are gradual fuel economy loss.

If the O2 sensors are bad what symptoms are present? Is it possible to have bad O2 sensors and not have the SES light on?

Yup. Mine dropped 1-2mpg ever a year with no codes. Replaced them and mileage came right back.

Cranky1 · February 15, 2007

It could be just the cooler weather causing a decrease in your fuel mileage. I have seen my self get 70 miles less to a tank of gas in the cold weather.

02 sensors are not cheap to replace if your looking for a process of elimination fix. These 4 wire connectors sensors have heaters built into them. You should have 4 02 sensors all together. bank 1 and 2, 1 just before the catalytic converter and 1 after the cat.

Bank 1 and 2 are the most important of the 4. I believe with a programmer you can turn off the 02 sensors down at the catalytic converter.

I have had a DTC P0135 heater problem with bank 1 on my truck, I can feel it when the engine is cold and it burns rich. That is the 1st thing I will fix once it comes out of storage.

I am not sure if the 02 sensors before and after the catalytic converter have a 4 wire connector with heater and they could be cheaper to replace if they are 2 wire connectors.

beretta01 · March 30, 2007

Does anyone notice is really big performance decrease if their bad also?

HyperBuzzin · March 31, 2007

Does anyone notice is really big performance decrease if their bad also?

My Jimmy was running like crap and I lost about 100 miles to a tank.

Replaced plugs & wires, not a bit better.

Replaced O2 sensors and everything's back to normal.

So yes, I noticed a BIG performance (as well as gas) loss.

beretta01 · March 31, 2007

Does anyone notice is really big performance decrease if their bad also?

My Jimmy was running like crap and I lost about 100 miles to a tank.

Replaced plugs & wires, not a bit better.

Replaced O2 sensors and everything's back to normal.

So yes, I noticed a BIG performance (as well as gas) loss.

Ok, thats good news because I got the EGR and Oxygen Sensor error code and I am getting horrible performance. I used to be able to peel out from dead stop, now I cant at all, lol, not that I really needed to anyways......

svensk · March 31, 2007

I just replaced my bank 1&2 sensors as they were tripping my SES. Just a warning you might need a shop to replace the one under your drivers side because the wireharness travels up between your 4x4 front drive shaft and the tranny. Impossible to reach unless you drop the shaft or have something special to reach it. I had a shop just install it for me after I did the other one myself.

Had them erase the code, mileage immediately improved and no more SES light.

If your O2's are out of range and setting a code your PCM will run in open loop paremeters which means you will be running extremely rich the whole time (that's why the fuel mileage loss). Your truck runs in open loop normally until the cats heat up to about 600 degrees then it starts reading the info from the O2 sensors.

jasonlaj · May 4, 2007

I just replaced my bank 1&2 sensors as they were tripping my SES. Just a warning you might need a shop to replace the one under your drivers side because the wireharness travels up between your 4x4 front drive shaft and the tranny. Impossible to reach unless you drop the shaft or have something special to reach it. I had a shop just install it for me after I did the other one myself.
Had them erase the code, mileage immediately improved and no more SES light.

If your O2's are out of range and setting a code your PCM will run in open loop paremeters which means you will be running extremely rich the whole time (that's why the fuel mileage loss). Your truck runs in open loop normally until the cats heat up to about 600 degrees then it starts reading the info from the O2 sensors.

i c this thread has been inactive for a while, but here goes...bank1&2 sensors...are those the ones before the cat??? also do i need to replace all four or just 2??? how do you test these???

thanks for the help.

i will keep searching as well.