2001 Pathfinder O2 Sensors

[cps2001path]

I have read on this forum and others that after replacing the downstream O2 sensors you need to have the OBD-II reprogrammed in order to keep from burning up the new sensors.

Is the dealership the only place to have the procedure performed?

What should I expect to pay?

TIA

[burns9189]

I just replaced mine havent had a problem since

[mda185]

This sounds like a dealership BS line. First of all OBD II is only the communication link between the engine computer and the diagnostic device used to read fault codes. I can't imagine having to reprogram an engine computer every time you replace O2 sensors. It is possible that the engine computer has some learned behavior in terms of fuel injection 'trim' that will impact how rich or lean your fuel mixture is for a short while after replacing O2 sensors but this should not cause you to burn them out. This scenario is much more likely for the O2 sensors in front of the catalytic converters. The O2 sensors downstream of the cats are only there to tell the computer if the cats are working properly or not.

What is being referred to as reprogramming is most likely just clearing the fuel injection 'trim' values in the engine computer's memory. This will happen automatically in a week with a daily driven car. Sometimes, you can also clear these values by pulling the ECU fuse and leaving it out for several minutes.

I would not pay the dealer any amount for reprogramming. If the engine ECU really needs to be reprogrammed, it should be covered under emissions warranty and/or a recall. If the dealer is just clearing fuel trims, don't pay for it. Driving will take care of this over a short period of time.

[Empty V]

I think what he's referring to is that at some point the ECM needs to be flashed because there is a new program that preheats the pre-cat o2's to increase longevity. At least that's what I gathered from reading the other posts about the flash.

Billy

[mda185]

Thanks for explaining that. I wasn't aware of this ECM upgrade and I will search the forum for more info. This still sounds like the kind of thing that should be performed free of charge because it involves the emissions control system. Have folks on this forum been paying for the ECM reflash?

BTW, just about all O2 sensors these days have heating elements in them for improved cold start characteristics. O2 sensors don't work right until up to a certain temperature. I am guessing that the ECM reflash changes how long the heating element is powered and this reduces the amount of time the engine is running rich after a cold start. Unburned hydrocarbons from running rich shorten the life of O2 sensors more than anything else.