Having trouble getting catalytic converter rediness ready to take emissions test all my other monitors are ready. i have driven on highway and streets contions. I have driven 55 mph on highway for 20 minutes. stop and go contions on streets

Usually between 5,000 & 10,000 miles on pontiacs

there is still a problem with
motor itself
the 02 sensors
the catalytic converter or the
engine emissions /gas .. filtering /re burn system

Generally speaking, the truck has to be driven at least 100 miles in various driving conditions including highway and city driving and at full operating temp. The mechanics are correct in saying there is nothing they can do to trick the system into thinking this has happened.
If 100 miles did not do it you may have to drive 2 or 3 hundred miles then try the test.
The purpose of the computer being "ready" is having used and tested all of the emission components for problems. Once the vehicle is driven far enough for the computer to use all of the components, and no trouble codes are set, the test is passed.
Even if you normally only drive in the city you still have to log 50 or 60 miles on the highway to satisfy the requirement for the engine computer.

****** your timing so it barely runs and have it tested again, i had to do this on a built motor i had in a pickup a while ago and it worked then. not sure if the testing standards have changed alot since but its an idea.

Has the battery been disconnected, or has it gone dead? Every time the battery is disconnected, all trouble codes are cleared, the check engine light is turned off, and all system monitors are reset. For the monitors to get back to a 'ready' status, the vehicle needs to go through one or more (sometimes quite a few) drive cycles.
When you go to the emission station, they check for codes, AND also check to see how many of your monitors are in a 'ready' status. (This keeps people from disconnecting the battery, and thus clearing any trouble codes, in order to pass emission tests).
If you have not disconnected your battery for a while, but the monitors are still not showing 'ready', you need to have a qualified shop check out your computer and other electronic systems.

HAVE GARAGE CODE SCAN VECHICLE.IF YOU ARE GETTING CATALYTIC CONVERTER FAULTS OR OXYGEN SENSOR FAULT CODE.YOU HAVE FAILED SENSORS OR VACUUM LEAKS. SOMETHING IS UPSETTING THE EMISSION CONTROL SYSTEMS.

This is the biggest flaw in emissions testing. It takes 4 tanks of fuel and 1000 miles of wasteful driving to reset the computer on the FORD TAURUS (I've got a 2000). So much for pollution control!

unhook the battery for about ten minutes... make sure you have the code for the radio (if required)

P0420 means Catalyst System Efficiency Below Threshold, Bank 1
It means that your catalytic converter, in the exhaust system is not working fine, as its emissions are polluting the air too much.

The catalytic converter is part of the exhaust system. The way to test this part is by doing an emission test. The two OBD codes that you are getting are already a test telling you that the converter must be replaced, unless an emission test done at a garage says the opposite.

This kind of problem will trigger the check engine light, and your car will also waste too much fuel.
You also risk to get in trouble if the car goes through an Air Pollution control, as the car won't pass an emission test in this condition.

To conclude, the Catalyst System must be replaced, the O2 Sensors are fine.

This is a repair that should be done at a garage, however you can find DIY instructions here:How to Replace a Catalytic Converter or you can get more detailed instructions, and step by step illustrated procedure purchasing a repair manual.

It needs a "drive cycle". Start & run it, highway speeds, and then pull over & idle several times, then do city traffic "stop & go" driving, and then sustained highway speeds again. This completes the readiness thest and satisfys all of the monitors.