do you need to recalibrate ECU after replace catalytic converter?

[rollingthunder6]

i recently purchased for my wife a used 2003 4-cyl Camry, a/t, 125000 miles, from a toyota dealer. Nice car. After a couple weeks, the check-engine light came on. I got out my Actron OBD II code scanner, which i used to retrieve a P0420 DTC. I researched that DTC on the internet and found out it is a "catalytic converter not performing to spec" issue. I erased the code, and it has not returned in the month since then. I dropped by the toyota dealer to discuss the issue w/ a service tech, who told me that altho i could replace the catalytic converter myself, i would still need to bring it by to them so that they can "recalibrate the computer" after the new catalytic converter has been installed. Back in the 60s and 70s, i had A LOT of experience working on VW Bugs, rebuilding Bug engines, even once rebuilt a VW bug standard transmission. So i like to think i know a little bit about auto mechanics. But back then, VW Bugs did not have catalytic converters, much less onboard computers. So i need to know: on MODERN cars, do you need to recalibrate the onboard computer whenever you replace the catalytic converter? I have both the Chilton AND the Haynes shop manuals for this car, and neither one of them mentions any such requirement. One further note: I found a TSB for this car on the internet, Toyota TSB EG024-04, relative the onboard computer and P0420 DTCs, but the tech at the dealar told me it does not apply to *my* engine b/c it was built after the Production Change Effective VIN (and that jives w/ what i concluded).

[gdanaher]

I built a lot of Type I and Type IV engines in my time as well, so I feel your pain! My short answer is that I don't know the right answer, but this is what I would do. If the MIL does not come on again, I would do nothing. Second, if it does, I believe it has a sensor in the CAT and it could be that the sensor is failing. I would check the sensor before replacing the converter. Much cheaper. It might be that you could pull the sensor and clean it, but in any event I would not be in a hurry to spend money. If, after replacing the sensor and/or converter you get a related error, then take the car in to look at the computer. It makes no sense to me that the computer would need to be programmed for this. It is already looking for a nominal value, plus or minus, and if it stays within those parameters then all is well.

[JohnGD]

A catalytic converter is a passive device. Did the dealer mean pressing the Clear button on the OBD-II/CAN scanner? Autozone can do that for free. Except maybe the dealer took the time to "explain" it to a typical owner?

If they know of other ECU programming defects then that's another story. Maybe ask them directly what they plan to do and why.

Originally Posted by rollingthunder6

i recently purchased for my wife a used 2003 4-cyl Camry, a/t, 125000 miles, from a toyota dealer. Nice car. After a couple weeks, the check-engine light came on. I got out my Actron OBD II code scanner, which i used to retrieve a P0420 DTC. I researched that DTC on the internet and found out it is a "catalytic converter not performing to spec" issue. I erased the code, and it has not returned in the month since then. I dropped by the toyota dealer to discuss the issue w/ a service tech, who told me that altho i could replace the catalytic converter myself, i would still need to bring it by to them so that they can "recalibrate the computer" after the new catalytic converter has been installed. Back in the 60s and 70s, i had A LOT of experience working on VW Bugs, rebuilding Bug engines, even once rebuilt a VW bug standard transmission. So i like to think i know a little bit about auto mechanics. But back then, VW Bugs did not have catalytic converters, much less onboard computers. So i need to know: on MODERN cars, do you need to recalibrate the onboard computer whenever you replace the catalytic converter? I have both the Chilton AND the Haynes shop manuals for this car, and neither one of them mentions any such requirement. One further note: I found a TSB for this car on the internet, Toyota TSB EG024-04, relative the onboard computer and P0420 DTCs, but the tech at the dealar told me it does not apply to *my* engine b/c it was built after the Production Change Effective VIN (and that jives w/ what i concluded).