Toyota Repair: P0420 code, egr system, cat converter

Question
Hi Ted.....I have a 96 Toyota Tacoma 4 Cyl. that had a P0402 code.  I checked all EGR system and all checked OK.  I replaced the EGR modulator and the light came back on.  I went back to Auto Zone and rechecked the code.  It now comes up with P0420 code.  I found that I have a cracked exhaust manifold.  Would this cause these both codes to come up.  Thanks

Answer
Yes, the exhaust manifold should be repaired or replaced first, the 420 is a catalityc converter code so this leak should be taken care of before the cat converter is damaged, after the repalacement of the leaking manifold reset the check eng light and see if the code comes back, if so then the cat needs to be replaced. It's not common for exhaust manifolds to crack so it would be a good idea to check for the cause of why it did, it may be running too lean or the EGR system failure could also be the cause.