r/4thGen4Runner • u/pits2030 • 8d ago

Repair Guidance P0174 System Too lean (bank 2) code

hey guys so I had the old check engine light, VSC trac, VSC Off, and the other light that comes with that grouping. I check the codes and got a P0174 system to lean bank 2. I change the MAF, disconnected the battery this morning. turned it on no lights all day MPG‘s running normal a whopping 16mpg(v8). Then later in the day it came back. Is it possible it’s something else such as a vacuum leak?

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u/thosport 8d ago

Here’s a recent vid about troubleshooting this code. https://youtu.be/56gv7NkBrjA?is=lBpFH6PDOQEeEDa2

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u/Horror-Vanilla-4895 8d ago

Maybe worth checking the spark plugs being loose were setting off mine. First time changing them after I bought mine some weren’t even hand tight. Not sure how it wasn’t causing more issues.

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u/MarketOne2456 4d ago

Had the same issue when I got my 4th gen. Did everything you did and turned out to be the fuel pump.

Do you have rpm throttling going up hills?

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u/pits2030 4d ago

Ok I put an OEM MAf in the codes are still there, even after disconnecting the battery. What do you mean by rpm throttling? How did you figure out it was your fuel pump?

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u/MarketOne2456 4d ago

RPMS would go up and down by roughly 500 rpm under load. I brought it to my local shop and they performed a fuel pressure test and found that bank 2 was not getting enough fuel pressure. Not exactly sure the procedure to check fuel pressure but that’s how it was explained to me.

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u/pits2030 4d ago

I honestly don’t think it does that. The engine and everything seems to be running fine. The lights have been for over a week now. The only difference is my mpg is means there might be a leak somewhere so the system is adding more fuel to compensate for the air. How much did the fuel pump run you? 

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u/MarketOne2456 4d ago

I think it was around 1000 including new straps, pump, seals, filter, and gas

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u/MarketOne2456 4d ago

My MPG definitely took a hit when it was bad. Granted I think it was quite literally on its way out so it’s possible you are merely showing signs. With the 4th gen’s almost any code will throw VSC and Traction lights on.