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.

 

Changed the fuel pump last night, still not starting and I’ve run out of ideas of what parts to throw at it next.

 

Stop firing parts, need to test stuff.

Is your security light next to the clock flashing with the key on? If so you have an immobilizer issue, if not continue through the next questions.

Does the check engine light come on with the key on?

Do you have a scan tool that can read live data? If so see if you have RPM while cranking.

Check if you have spark.

See if you have power at the fuel injectors on the Black/Red wire.

 

Have zero rpm and data when starting. Unfortunately I have no security light next to clock because the previous owner did diy replacement for the dash. Do have spark.
I’m testing the electrical system right now, there is a directed electronic 3100 that looks like a toddler wired

 

So you lose communication when cranking?

Not sure what this means? What did they replace it with?

Not sure what this is either, got pics of it?

 

https://www.directeddealers.com/manuals/IG/Avital/N3100%202011-12%20print.pdf
I found the manual to it, not sure if it was the problem but bypassed it still didn’t start.
I borrowed a better code reader and it still says it’s only the p0420.
Tomorrow I’m just going to go through and re test everything with a battery just to rule out a short

 

Idk if this was stupid or not but I disconnected the main fuel lines and lead them into a bucket and attempted to start and no fuel came through. Would this be indicative of a problem of a fuel delivery/electrical problem or me being a dumbass?

 

Well that tells us your fuel pump isn't running (or if it is it isn't pumping any fuel).

Try jumping pins 3 and 5 (the 2 larger pins) of the C/OPN relay with the key on and see if you get fuel.

 

Jumped pins 3 and 5 with key on, nothing happened, did read 12v in pin one if that helps.

 

Check connector IB1 Pin 8 (Black/Red) behind the left kick panel for a burnt pin, if it's not burnt check if you have power there with the relay jumped.

 

No burnt pins, I assume you mean power on the C/OPN relay. Testing it now

 

basics.....
did we verify spark?
did you spray brake cleaner down the intake while cranking?
If it starts, its fuel....
Did you try starting with the exhaust at the pipe to the exhaust manifold disconnected so it can breath.....?
Your can may have been so F'd up, it could have plugged the rest of your exhaust & you have no idea...

Then theres always compression, I good tech can listen to the rhythm of a engine just cranking & will know if it has internal issues or not...

 

I might be doing something wrong or confused but there was no power when testing. In the c/opn the volt meter before only read 12v power in pin #1 so idk how would power Ib1 when the relay is jumped. Would this mean the pins themselves (#3 and #5) are a problem or I’m making a mistake somewhere.

 

Tested most of that already but no fuel to the fuel lines is my primary concern right now.

 

Ni idea, not giving us a whole lot of useful data that truly means anything.
You state possibly starter or fuel problem, well those are totally 2 different systems & they symptoms aren't the same..

If it truly is a fuel issue, you crank engine while spraying brake cleaner down the intake, it will start....

Then you need to find out why...