Codes P0420 and P1423, car dies while driving
 

While driving and shifting to the next gear the car (318ti - 5spd) revved then stalled. I was able to start the car and the same thing happens. Waited for 10-15 minutes started the car and I was able to drive it to a parking lot and did some diagnostics. I was able to retrieve the code P0420 and P1423. The engine runs fine while in neutral. Any clues would be helpful.

robbed off elsewhere:

A code P0420 may mean that one or more of the following has happened:

* Leaded fuel was used where unleaded was called for
* An oxygen sensor is not reading (functioning) properly
* The engine coolant temperature sensor is not working properly
* Damaged exhaust manifold / catalytic converter / exhaust pipe
* Retarded spark timing


u might also find this usefull...http://www.troublecodes.net/OBD2/Pcodes.shtml

That 1423 code looks like it could be the Secondary Air Pump. It's quite possible that you just have a vacuum leak. I guess the best thing to start with is checking all the hoses in the engine compartment. There are probably test procedures for the air pump in the Bentley manual, but I don't have mine handy. Let us know what you figure out.

Yeah, The first code is a cat efficiency code. It means the rear sensor is telling the computer that what comes past the cat is too rich. If it is not coupled with a code for the front sensor, suspect rear O2 sensor or cat failure. It seems that it is coupled with a secondary air code (I will check that tomorrow) which could be a secondary air hose leak, a secondary air valve malfunction, vacuum hose fell off, or secondary air pump is toast (all common problems,) all of which can cause a code for cat efficiency. I suspect vacuum leaks or cat failure as possibilities because a faulty secondary air pump will not cause the car to cut off. A vacuum leak or cat with guts broken loose can.

I reset the codes. Checked for vacuum leaks and the secondary pump. Did not find anything suspecious. I was able to drive the car home and to work. I can hear the cat rattling so I need to have it replaced.

I took the car to a BMW Dealer and they replaced the catalytic converter under warranty. My 318ti is all happy now. Thanks for all the suggestions.