Could P0121 and P0430 codes be comming up due to other issues with my truck?

SOURCE: 2002 Silverado code PO174

After fighting with mine (2003 GMC 5.3 liter), I believe I have it solved. Mine was throwing P0171 and P0174. Also, there was an occasional p0101. I had a rough idle sometimes right when I started it, but usually after 5 minutes when the fuel system went in to closed loop mode (about 200 RPM swings at idle that slowly went away). Days below 10 degrees were much worse.

I cleaned the MAF sensor, checked fuel pressue, changed spark plugs, and cleaned the throttle body. The code basically means that more fuel is being dumped in by opening the fuel injectors longer. The code is set by the long term trim on the injectors be over 23% (opened 23% longer than they should be based on sensor readings). The extra fuel allows the engine to run with the right air to fuel ratio (not necessarily lean as the code suggests). Causes could be low fuel pressure (from pump, fuel regulator, clogged injectors, and such). Running a scanner on it for several days, everything looked normal.

That is all background. The other cause is that air is being introduced into the intake after the MAF sensor. Extra fuel has to be added for the air that the MAF does not see. I did some digging and found out that the gaskets between the plastic intake manifold and cylinder heads are prone to leaking. I tried to spray throttle body injector around where it might leak to monitor the engine speed, but the air leak seems to be less on warmer days and leaks can occur on the inside edge of the gasket where it is hard to reach with the spray (there are foam ends that open the inside edges to atmosphere). I replaced the gaskets and my long term trim dropped to about 6% from 10% on warmer days to pegged out at 25% on cold days with a cold engine. The work isn't too bad as long as you are patient enough to get the plugs off of the ignitors. I have yet to test it out in cold weather, but I am pretty confident.

SOURCE: P0300 - Random / Multiple misfire

The .030 may cause a too rapid burn time condition. And Yeah, .060 is standard GM on almost any make/model nowdays.. It may be one of ur coils.. but that would show an individual cylinder.. Try the .060's and let me know.. esp if it wasnt doing it before

SOURCE: 98 cavalier 2.2L cold misfire/no start

You may be looking at dirty injectors. I would run a good quality (something like Wynns or Redline) fuel system cleaner through, following the directions on the bottle twice. Which usually means adding the bottle to a full tank of fuel, and then adding another bottle after a second fill. Check for improvement, this will cost under $30, vs a trip to a mechanic. A friend of mine had a 2.2l in a sunfire that did something very similar and a good cleaning cleared it up completely. Unfortunately, he spent $300 at a mechanic to find out.

SOURCE: my bully dog pmt shows code po678 glow plug number

PIP3586E

This is a bulletin number for a glow plug issue. If one tests bad you will need them all replaced.

If you have less than 100k miles on the truck you should still be under warranty.

SOURCE: code p0121 TPS

THERE IS A TP SENSOR BUILT INTO THE THROTTLE ACTUATOR. THESE TRUCKS HAVE BEEN KNOWN FOR A FEW PROBLEMS IN THIS AREA. THROTTLE ACTUATOR IS NOT SERVICEABLE. THE THROTTLE BODY WILL NEED TO BE REPLACED IF IT IS PROVEN FAULTY. THE APP SENSORS ARE LOCATED IN THE GAS PEDAL MODULE. THESE SEND SIGNAL TO COMPUTER TO TELL IT WHERE YOUR FOOT IS, THEN COMPUTER SENDS COMMAND TO THROTTLE ACTUATOR TO OPEN OR CLOSE THROTTLE BASED ON THIS INPUT. THE SENSOR IN THE THROTTLE ACTUATOR DELIVERS A MESSAGE BACK TO THE COMPUTER TO TELL IT WHAT THE ACTUAL THROTTLE POSITION IS. IF THESE SIGNALS DONT MATCH(WHERE THROTTLE IS COMMANDED AND WHERE IT ACTUALLY IS)THE CHECK ENGINE LIGHT WILL ILLUMINATE AND THE VEHICLE COULD GO INTO A REDUCED POWER MODE. HOPE THIS HELPS YOU!