P0420 truck not starting:

This is my first post so sorry if my formatting is weird but my 2006 base model Tacoma popped the P0420 code and after replacing multiple parts it longer starts. Here is a list of most of the replacements all of which seemed to temporarily fix the issue before popping the code a few days later:

PCV Valve, secondary air injector, pump and valve, fuel line, regulator and injectors, spark plugs (twice) and coils, battery, catalytic converter, both o2 sensors.

I’ve checked for exhaust leaks, and tested fuses and relays.

I had multiple random engine misfires as well as a few other codes that have been fixed and thus the reason for all the replacements, none of which have returned.

Before it stopped starting completely (0 rpm when attempting to start) it would take a few tries and flooring the gas pedal. It would idle rough and hesitate when accelerating. When the front was jacked up it also wouldn’t start till on level ground.
Possibly unrelated on two occasions on 3 hour road trips the battery warning light would turn on and once died on me but these incidents were about a year apart and possibly a symptom of the previous owners shotty diy wiring for sound system and kill switch but felt it was important to mention just incase.


I’m leaning towards potential fuel pump or starter issue but know there it could be a number of problems and would like to hear from y’all where to start to hopefully solve this mystery.

 

Holy parts cannon

Not really sure where to begin, 95% of the time P0420/430 is a faulty converter but we can ignore those at the moment since the truck is a no start.

My first question is does it crank and not start (engine turns but does not fire) or does nothing happen at all what you turn the key?

 

Welcome to TW..

 

Does it crank over normally but not fire?

 

It does crank but does not start

 

This sounds like a fuel delivery issue (degraded pump, clogged filter sock, fuel hose leak inside the tank, fuel line restriction outside the tank...)

If it cranks fine, this rules out the starter, security system, and neutral safety switch.