Truck stuck in limp mode

So it has been like this for awhile but I've attempted to fix it and now I'm stuck, truck shut off one day while leaving work when I started it back up it had check engine light and was in limp mode, replaced MAF, air pump, and both 02 sensors. If you try to clear the code it just cuts right back on when u start the truck and if you clear it while running it cuts off for half a second then turns back on and the light comes back on, I've checked all grounds and fuses, my last resort is the ecm, unless there's something I'm missing should I buy a replacement ecm online and replace it and hope it fixes it?

 

Code is p0171 by the way and that's it no other codes

 

P0171 is a lean code (not enough fuel/too much air), have you checked fuel pressure?

 

I can when I get home tonight, it just confuses me how it was instant and not an intermittent issue

 

With that code and those symptoms I would definitely want verify fuel pressure (should be 40 psi) is good before throwing anymore parts at it

 

Yeah I 100% get what u mean, I remember now the reason I even replaced the pump and MAF was because the truck did throw a code for the pump and I saw p0171 could be cause by MAF so I replaced it and the 02 sensors where just something I did because they had a deal on rock Auto. But when I get home I'll check that, if it is below the required psi what would be my next move?

 

how would one check that?

 

From what I'm seeing on other forum posts you have the make a t and use a specified tool from Toyota to check it while others say just put a pressure gauge in line and get a reading don't know if they are very correct or not, I have a snap on scanner would the truck possibly relay to it the fuel pressure ik there fuel stuff in there just haven't gotten that deep with it

 

Fuel pressure requires special tools and adapters sadly.

I pull the lead line off and put a hose into a bottle to check it really quick. The disconnect should be on the drivers side of the engine bay.

Lean codes and no power usually means fuel.

There is no code for fuel pump as a reference.

 

Well from what I was reading if you check it with a regular gauge in line it dead heads the fuel pump and causes higher readings so therefore I can check it and if it's low I'd know definitely something is wrong although it makes no sense my truck has 97k on it and the fuel pump is already failing?

 

you need a setup like this to tee into the line where it goes from the body to the engine.

$31 BETOOLL Fuel Pressure Test Kit 0-100PSI with 9.497.896.30 Fuel Line Fittings

Amazon.com: BETOOLL Fuel Pressure Test Kit 0-100PSI with 9.49,7.89,6.30 Fuel Line Fittings : Automotive

 

Alright, I went ahead and ordered it and it will be here Sunday, until then is there anything else I can check?

 

You should also check for vacuum leaks under the hood.

 

I’ve never seen a P0171 cause a limp condition. Maybe a bad/dirty MAF.

 

My bad I forgot to mention I did that with a can of starting fluid and yielded no results

 

A quick google search found this.

Well, I was gonna copy paste but it says copyright etc.

 

I hope not, it was a brand new Denso maf from toyota

 

That leads me to believe there is a problem within the fuel system.

Here is a picture on how to check fuel pressure using the Toyota special tool.

 

Thanks, I ordered the tool and it will be here Sunday it's just odd to me though how it was instant and aswell the truck was running fine leaving work but then while idling it shut off and has been limp mode ever since, that's why I suspected ecm or wiring issue but hopefully it's a simple fuel supply issue and recommendations on what it would be if the fuel system wasn't getting the correct pressure?

 

Almost forgot: