Fuel Pump Relay Buzzing 00 Tundra

Hey all,
I have a 00 tundra 4.7L V8 throwing a P0161 and P0161 P code. The trucks fuel pump relay also buzzes when shut off. The truck starts up fine and the relay buzz shuts off while started. Then the buzz comes back after the truck has been off for awhile. Replaced the relay like for like but the buzz comes back. Tested the resistor resistance at 0.8. I still have the factory resistor and fuel pump. Trying to figure out if it's something else before I replace those.

I bought new 02 sensors to pop in to try and tackle the P0161 issue.

Recent work - I just replaced the valve cover gasket, spark plugs, and clock spring. I had a horn issue that wouldn't shut off, which I read could've been a grounding problem due to rust. I rewired the cruise control based on another forum which fixed the horn.

Not sure what's related to what. Any help appreciated, thanks!

 

Man, I distinctly remember someone else complaining about this, and I swear it was something really stupid like a blown fuse. It's popped up a couple of times, but it's not sticking in my brain what the issue was.

Hopefully you bought authentic Denso sensors and didn't cut harnesses.

 

New Denso everything. Haven't cut any harnesses. I've probably read a dozen other threads, no idea.
If you remember, please lmk! Thanks.

 

Oh sorry didn’t mean to imply the buzzing was related to harnesses or brands of hardware. I’ve just seen several times in this subforum where people complained of - I think it was when a specific fuse being pulled or blown - a specific relay would buzz or click repeatedly (which I’m sure can’t be good for the relay, knowing what happens inside a relay), but it would stop if they disconnected the negative battery terminal and reconnect it.

I just can’t recall if it is the fuel pump relay or the starter relay, but this specific thing, I know I’ve seen it. I struggle with memory recall on certain things and haven’t have time to bang the search and look. If I did, “clicking” or “buzzing” would be high on the list.

 

This won't be a fuse problem by no means but definitely could be a ground problem, as usual with Toyotas negative feed circuits to energize certain relays.

Given the EFI relay energizes the C/OPN relay which then energizes the FPR(fuel pump relay), if you pull the C/OPN relay when it's buzzing, does the FPR quit buzzing. Likewise, if you pull the EFI relay when FPR is buzzing, does the FPR quit buzzing.

 

Here we go, a couple examples of what I'm talking about, 1st one has a video with the sound:

https://www.tundras.com/threads/video-weird-no-start-buzzing-sound.87857/

https://www.tundras.com/threads/ste...h-beam-switch-not-working.60120/#post-1576846

And I distinctly remember we helped someone on here recently whose relays were buzzing but would start/stop when unplugging the camshaft position sensor or crankshaft position sensor. Pulling a battery terminal and reapplying with either stop or start the sound. I'm been struggling with brain fog since Saturday (medical issue), so I'm fighting to recall.

In no way am I saying either of these are remotely related. And @BubbaW definitely agree with you to check all grounds, have the battery professionaly tested for volts and amps, and to check/reseat the battery terminals.

I'm only sharing that 'buzzing relay' has definitely been a consistent "weird" symptom folks have reported in the '00-06 Tundras, it usually ends up being the fuel pump relay, and it rarely ever has anything to do with the fuel pump itself.

 

Glad you mentioned that because it reminded me I did not ask what he meant by...."Replaced the relay like for like but the buzz comes back" ....as in what kind of relay was used as replacement.

 

Good catch, I missed that.

I remember a handful of people on here looking for help, who we then found out had bought store-brand or "universal" relays for starter and fuel pump and had major problems which ended up being "wrong relay".

I get it, the relays from the dealer are astronomically expensive. Any time I hit the junkyard and see the engine bay fuse/relay box still intact in a truck, I'll raid the damn thing.

 

Thanks guys. I replaced the 02 sensors yesterday which fixed the P0161 code.
I replaced the fuel pump relay with the same part number w/ Toyota brand fuel pump relay. The buzzing still stayed on with the truck off and new relay, so I disconnected the negative and let the truck sit overnight thinking whatever the issue is might reset itself. Sure enough, when I reconnected the battery this morning, there was no more buzzing.

So buzzing gone and code gone. Before reconnecting the battery I did make sure the EFI and C/OPN relay were snug. The C/OPN seemed like it might have set into place when I pushed it in more, so that could have been a partial culprit.

I'll let you know if the problem comes back and revisit your suggestions. Thanks again!