Fuse block/ Harness removal?

Over the past 12 years owning my 2005 Tundra SR5 DBL cab, its had very random and intermittent no-start scenarios that I could never pinpoint but they would suddenly fix themselves after much useless work and circuit checking inspecting by your truly.

well recently I was doing some inspecting for No-start scenario and found when I grab the main wire harness and move it, I can hear relays clicking and the fuel pump turn on and pressurize and suddenly the Starter Circuit works again. Also a steady humming sound that I don’t recall coming from the intake/ starter potentially?

I’ve got the fuse block/ harness apart and definitely have problems with the STA relay because as I wiggle it side to side the Starter Circuit cuts in and out causing the OBN/c relay to open and close. I can’t figure out how to attach a video, but the relay starts clicking and the fuel starts flowing, then cuts out.

I’m wondering if anyone has ever replaced the main fuse block/harness and just how much of a PITA it is?

I know it’s seems wild to replace the whole harness for one faulty/loose ray connection but I sense there’s other issues with this harness as well because of all the electrical issues this truck has had.

 

A number of people have been thru it. A couple of more-active folks I can think of, off the top of my head, are @455h0le_dachshund or @Sirfive (I forget), @daveeasa and @RUSTYNUTS.

Mostly because leaks from the windshield and a-pillar into the fusebox, which rot out the fusebox, is such a pervasive issue in these trucks that we have it in the megathread, and there are gaggles of threads covering that damage (pics & pics & pics), it happens a LOT. Sometimes but far less frequently with the ECM behind the glovebox (pics, pics).

 

I'd just add, sometimes those leaks don't always hit the fusebox first. Sometimes they'll rot out wire connectors between the kick panel and the steering column like this: https://www.tundras.com/threads/abs-sensor-speed-control-sensor-or-both.143136/#post-3995062

Those two things are what you need to be looking for. I would almost guarantee you, one of the two is your issue. And if so, you really need to find the source of the leak, or it's going to happen again.

 

Its a pain, but doable if your patient. I had to use a mirror to reconnect everything. Alot of patience. I had to rage quit the first day, and try again fresh & ready.

 

I haven’t done my cowl clips yet. Still on the list to do. Less of a concern now that I park inside.

I haven’t replaced harnesses in my truck either.

I have replaced the integration relay (in cab fuse box) and the alternator fuse (blew it being a dummy with the alternator upgrade and swapped to a 140 since my alternator is 150A but I’m still due for big 3 someday.)

If a relay clicks with hand manipulation of the harness I’d zero in on that. Maybe tighten terminals before thinking replacement? Steinfab garage had a cute trick where he rotates the male spades 10-25 degrees to make more contact. That’s an easy way to confirm the specific problem at least. Not saying my OCD would be ok with twisted spades.

 

Thanks very much for the information and insight.

sirfive - good to know it’s possible , but might push me to the brink of my sanity…is there a bunch of connections up under the dash? I’m also dreading removing the new harness from the donor vehicle.

shifty- i will definitely take a look at those connections and maybe give them a smear of some dielectric grease. I have never seen moisture in that area before.

daveeasa- Yeah I agree, I am having a tough time not keying in on the c/OPN relay being activated by the pink/grey wire for the STA relay. Really wish it was possible to upload a .MOV file to this site. But the small pink/grey dot wire for the STA relay clicks when I barely touch it so something is goin on with it and would explain my random no Start Circuit issues. I’ll maybe bend the tabs on the relay? These fuse boards don’t look like they’re designed to be “fixed”

 

Label each plug with a number and mark which number goes where, because your connecting things blind.



pic is w/o DRL, i dont know what the difference is, but find a diagram for your exact truck.

 

Kick panel plugs all look like new.



truck is starting consistently again but going to start looking for a new harness

 

Help me understand, can you show me a picture of the harness you're wiggling to get things to start, and hearing relays clicking?

 

It’s the fuse box itself . Narrowed down to this wire heading into the STA relay.

 

Ah! Engine bay fuse box. I thought you meant the in-dash fusebox. Sorry, I must've missed that bit.

 

De-pin and tighten? Or twist? Or repair wire?

 

I’d really like to de-pin and tighten but can’t figure out how to remove the pin outlet(?) without breaking something.

also, the outlet is not touching anything else, so why the heck is it activating random items from the starting sequence (aka fuel pump) when moved?

again, any advice appreciated!

 

Not many, but a couple times on here, we've seen where stuff inside/under the engine bay fuse/relay box is arc'ing, and the spark from the arc is either causing shorts down the line, or spiking the system. And stupid results happening. The one that sticks out in my hand was this one guy whose 140A "ALT" fuse had a short in the receptacle. When he was finally able to get the 140A fuse pulled, it had a black bite mark clear out of it. The symptom was 'no start'.

 

Here it is: https://www.tundras.com/threads/charging-alternator-problems.97131/#post-2469357

I guess the problem was no charge? I didn't read back through it but ... 140 ALT, makes sense, no charge. But yeah, just showing an example, you may have similar arc'ing happening. It's supposedly confusing and/or a bitch to get the fuse/relay box out without breaking shit. Something about lifting up the plastic outer, and dropping the fusebox out from under? I forget, but I've seen someone on here explain it.

 

Thanks Shifty! That 140A fuse is one thing I haven’t checked yet. Not even sure where exactly it is. Truck is starting fine again………for now.

 

Fairly certain this is it, right next to the spare fuses. But your truck may be slightly different, given I have AC and you have DC. Fuseboxes do change slightly based on year and cab type.

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https://www.youtube.com/watch?v=iNsNZBt3rCU

 

I mean it’s a pain but it’s not rocket science either. Take your time, make it loose, don’t break things. Definitely remove battery, not possible without that. All you really need is the correct replacement fuse.

 

Ok ya in that case I do believe I checked that fuse already. In the 2005 DBL cab it’s a large clear plastic fuse that looks like an old cassette. It’s fine.

 

What you're posting a pic of is a fusible link or "multi-fuse".

The part number is typically what you posted, but you'll want to verify in the EPC if your part number ends in 0C030 or 0C040, you may also be able to visually inspect. You posted the 40 part, here's the 30 version part.

Never trust Toyota Parts Deal. But moreover, never buy from TPD. You may get lucky on an order or two, but they'll eventually fuck you over like they have everyone else here and on the sister site, TacomaWorld. Posts galore on the topic.

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Ok thanks, the pic was just for reference. I’d never heard of that site. But I’ll steer clear in the future. So would you say my truck does have that small copper band fuse that was rotting out in that other thread?

 

Show a pic of the fuse/relay box next to the battery on your truck.

 

Ok, so it looks like you have both multifuses, the green one you posted, and the black one I posted. The DC block looks so much easier.

Is that an SAIS bypass I'm seeing in the background? I'm asking, because add-ons like that would be really nice to mention when you're diagnosing issues. Bypasses can create collateral issues, you know.

 

Yup that is an SAIS bypass wire to the relay. Sry I didn’t think that wire could be the culprit. Weird I’ve had it removed for a couple days now and I’m still not getting a Check Engine light, which is what I thought that wire was for

 

Some people (stupidly, IMO) bypass SAIS totally before any problems arise, or alternately when they get any code related to SAIS. It could be something as simple as a vacuum hose loose causing the code, or the truck could be part of the TSB where certain cold-temp situations will lead to SAIS throwing a code (the TSB is linked in the Megathread, one of the codes is P2445, I think), and there's actually no issue with SAIS, it's just a known thing that happens in extremely cold weather.

Anything that modifies/tampers with OEM systems could lead to secondary issues. Don't think it's responsible in this case. But it's worth mentioning. I don't think the truck will start w/o the MAF, so like, that bypass probably intercepts the MAF, so if something is shorting in that line, then ... well ...

 

That’s interesting. I believe I installed that kit about a decade ago shortly after buying the truck. I had a few codes that kept popping up, P2445 sounds familiar, and they never returned after installing it. I live in about as cold conditions as you’ll find and haven’t seen the P2445 come back.

I’ll do some more inspecting on that purple wire, but likely going to leave it disconnected until I get an engine light again.