I had the code for a while. Besides that I had a misfire (changed coils) and RPM dropping way to low (sometimes stalling) when coming to a stop + low idle (almos 500rpm). Last week I took the car to the dealer to do the TSB work. I also complained about all other stuff and they said they would look into it. Few hours later I call them to check on the status and they said everything was ready BUT they (what do you think I'm gonna say?) COULDN'T DUPLICATE any other problems that I described. I pick up the car, drive around and so far my RPM never dropped. Idle rose up to 800rpm or so, but that's fine.
So my question is, could the P0420 code cause any other side effects? Or do you think they just rose the idle?

P.S. - it's the 3-rd day and the problem hasn't come back yet...

 

i have that code 0420 and my car makes a rattle when past 3000rpm from running lean due to a o2 sensor. What did the dealer fix? what was the cost?

 

Quick question, what is TSB?

 

tsb: technical service bulletin

and as for the P0420 code, I've been on that for the past three months will absolutely no side effects besides the annoying light. My gas mileage has not changed and the car drives fine

 

the TSB that I was talking about was just reflashing the ECU with the new version of software (or whatever they call it). It was done for free since the car is still under warranty.

Larrio: well, that's exactly what I was thinking but apparently they either did something else besides the flashing, or there was another error somewhere else in the old version that caused incorrent sensor readings (my guess would me MAF).

 

hmm.... you could be right. I know that when I was at TS for the ECU testing, I had a coil misfire code when they tried to run a older version from a spare ECU on my car. I believe the p0420 is ver.16 and most 5th gens run ver.14 and ver.15.