a few codes and a few questions

So, the galant has been going through a few things lately. The latest is the brand new alternator that's less than a year old is taking a crap on ,e so back to Autozone it goes. The next is my check engine light has been on for awhile so I had the codes read while they were testing the alternator and she threw 4 of them.
p0401 Insufficient EGR Flow Detected
p0421 Warmup Catalyst System Effieciency Low( Bank 1)
p0551 Power Steering Pressure Switch Circuit Malfunction
p0734 A/T Incorrect Fourth Gear Ration

I'm assuming that one or 2 of these codes are related; I knew about the 1st which I thought I had already fixed but the power steering code is new to me, and I'm not sure about the tranny code because as some of you may know that I was having tranny issues before and I swapped to this one. If anyone could steer me in the right direction for the last 2, I would really appreciate it.

Diaz

I just got rid of the first code, try taking the EGR valve off and cleaning it really good with carb cleaner/throttle body cleaner to get rid of all the carbon build up inside..I did that and the code came back on so I had to replace the EGR control switch/Solenoid and that cleared the code.


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