pdtass

I have 76K mi on my 2000 GLE and went to the dealer with a SEL P0420. Thanks to this board I was able to have them cover the pre cats. They also replaced the main cat because they could not get the thing off without ruining it. I did have to pay for two new O2 sensors ($300 with tax) but they credited the $90 to pull the code.

Do you think they replaced the O2 sensors simple because it is difficult to remove them or do they go bad and are the ultimate reason the precats fail on cali maximas. The car definitely has more power now.

I originally was going to order a new Y-pipe and main cat assembly from warpspeed ($285) but didn't want to deal with cutting the main cat out (bolts were rust in) and risking breaking one of the exhaust manifold studs. As I understand it the warpspeed Y-pipes do not contain precats. does this effect the O2 sensors since the up and down stream sensors would have only pipe between them and probably register the same reading?

The dealer did not replace the small front elbow section (probably the front precat) but they did remove the heat shield from this section and did not replace it. Is this a potential issue? Nothing is around it that could get heat damaged but could puddle water rapidly cooling the pipe cause damage?

Thanks