I have a 99 expy and the Service Engine Soon light came on yesterday... I had my wife stop and autozone and get it run and they told her it was
P0133 and P1131
They both seem to point to the O2 sensor.. Is it safe to assume I should just change that or could there be another issue?

 

Front sensor on passenger side is getting lazy in response time.
It is designated as OX2-11. This means bank 1 and the first one away from the motor.
Won't hurt anything but get less fuel mileage and higher HC emissions until changed out.
Good luck.

 

Good Luck? Is this tough to change or hard to get to? Is this gonna be a big problem for me?

 

No.

Blue's response was meant as positive reinforcement - he is truly helpful, no-BS kinda guy ( unlike me LOL!)

Not difficult.

Approx $50 from AutoZone. Ensure you get a Bosch unit.

You can Search here - lots of info on how to change one.

 

In that case thanks for the info Blue. I was under there yesterday doing an oil change (which turned into a mess) and saw a few o2 sensors and I think I saw the one that needs changed. But that is the consensus here? that changing the sensor should fix the problem. I am at about 91k so I would assume its due anyway.

 

Yeah - they do get lazy. You may want to consider doing the other bank's front unit as well. These two control your Air/Fuels.

I advocate a 30k change interval ( fronts only) based upon some advice from others - but some well-respected folks on here will differ - your call.

oh, and ... Good Luck! LOL!

 

Well I guess its off to the parts store.. I figure I will just replace both since I am approaching 100k anyway.

 

Lazy is a term used to indicate the OX sensor is not responding to a PCM test to see if the sensor is detecting a 'purpose' rich or lean condition imposed by the PCM program.
The code discriptions explain this if you get to see a better code chart.
I would change both front sensors for best procedure at the mileage you have.
Causes may be the gas you buy, additives you might use etc may have coated the sensor and blocked the diffusion that goes on in the sensor's ceramic porus structure.
If this diffision is inhibited, the sensor become slow/lazy or unresponsive.

 

Actually, a lazy sensor is one that no longer switches cleanly or promptly.

The lag or failure is very visable when graphing the O2 sensor voltage.

Personally, I replace 'em only when they fail.

Steve

 

My MPG are down and I dont know why. I have 73k on my 03. I have already invested in new O2 sensor and have been wondering is this is the reason for my problem. No codes and the truck runs great. I recently change my fuel filter also.