My 01 was throwing a P0138 and P0139 code (O2 sensor on its way out). I have both rear sensors on order, and will replace them once I get them. I know there is a TSB out for these, and after replacement there needs to be a computer reflash to "relax" the parameters for the sensors.

However, Im also going to be replacing my MAF, and Ive read most people think that there needs to be a reflash once that is replaced (I dont know if its to "clear out" the ECU values, or if there really is updated code for the MAF).

My question is if these are two separate flashes, or if one or the other covers both the MAF and O2 sensor code. Also, does the ECU *need* to be reflashed after MAF replacement, or would just resetting it by leaving the battery disconnected for an extended period suffice?

My mpg has just tanked (no pun intended) so Im guessing its a combination of both (I get engine hesitation when cold, so Im thinking MAF, and of course the P0138/139 indicate O2 sensor(s) ).

Thanks in advance.

-Chris

 

im pretty sure that the reflash is only needed after the 02 sensor replacment to correct the problem that made them go out. you have to go to the dealer for the reflash anyway, you could just ask them.