PO174, PO171 and now won't start (4 Viewers)

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Joined
Jun 2, 2023
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Missouri
Hi folks, looking for some guidance here.

My 2002 threw 2 codes at me a couple weeks ago, a PO174 and a PO171, which I assumed was a leak in the vacuum lines or a bad MAF sensor. I cleaned and swapped the MAF sensor with my 01 Tundra (benefit of having two vehicles with the same engine) to rule that out (no change), then pushed smoke through the engine (didn't find a leak), replaced all 4 O2 sensors (no change), and finally replaced the fuel filter. This has all been over the past couple weeks with it sitting and I went out to test the fuel pump and my engine won't start at all. It just makes a single click, the lights go dim when the key is turned and nothing. I thought it was the fuel pump safety switch but I made sure that wasn't the issue and there's still nothing. I'm still assuming it's an electrical safety feature that I need to reset since the starter isn't firing and it's not cranking.

I did not disconnect the fuel pump connection when I did the filter swap because that wasn't in the tutorials I found, but now that I'm digging deeper I see that was an included step in the TSM and while I'm worried I got air in the line, cycling the key to prime the pump and purge air isn't getting me anywhere. Am I supposed to loosen the nut on the fuel filter like you do to bleed brakes or is that not the issue?
 
There is no need to bleed the fuel system, the reason they want you to disconnect the fuel pump is so fuel doesn't spray all over your hot exhaust manifold, catch fire and then you sue them.

By a single click I assume you mean the engine isn't turning over at all, if that's the case, the starter is bad.
Single click, lights dim while turning the key means the starter is taking all the power but won't turn over. So it's bad.
 

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