CEL codes

[angman]

Hi guys, I need some help here. My CEL came on and I broguth it to a shop. the codes that came up were 1123 and 1125. My friend at the shop told me that it was related to the 02 sensors and replaced 2 out of the four for me and tuned up the car as well.

i picked up the car and it runs much smoother now and no more strange noises. However, the CEL light came back on again. Not sure what the codes are yet but I will find out. the guy at the shop told me he replaced 2 of the 4 sensors. Is there a way to tell which ones need to be replaced? Do all 4 have the be replaced at the same time? My friend is in the middle of relocating his shop so all his diagnostic equipment isn't readily availabe and his OBD reader that he currently has on hand doesnt seem to fit the relay on my 97 boxster for some reason. anyone know what those codes mean?

Thanks

[Jaxonalden]

I don't know what they are yet but I will as soon as I get my scanning tool. About the O2 sensors, your friend changed out two? Did his diagnostics say you had two go out? Not to dog your buddy but it sounds like he changed out the wrong one. Two O2 sensors going out at the same time then possibly another one (we don't yet until we read the code) sounds too much like a coincidence.

[angman]

Thanks i appreciate any kind of help.

The car runs and sounds great. Not sure why the CEL light came back on yet. My buddy is actually a very good tuner and knows 911 engines inside out. He does many engine swaps etc. as well. Maybe he was trying to save me some money by swapping out two sensors. I am not sure.

The problem is that he is just in the middle of relocating his shop so he doesn't have all his diagnostic equipment handy.

[tholyoak]

You just wasted money on replacing sensors that had nothing wrong with them. 1123 and 1125 are mixture errors. These are lean threshold limits being exceeded. What that means is your car is running rich and the computer has reached the limit in order to get the O2 sensors to read in range (does this by shortening the injector pulse). Probably a MAF problem. MAF is probably giving too high of voltage for a given amount of air and thus the computer thinks there is more air going in the motor than there actually is. Therefore, it is running richer than it should be and has to shorten the injector pulses over what the maps say should be for the conditions. Oxygen sensors are just reporting the condition, they are not the cause.

-Todd