2000 Tundra V8: Horn Relay Location

Hi Guys

I'm diagnosing an intermittent horn issue and want to rule out the relay first but it's not marked in the fuse/relay box under the hood?

thx

bob

 

Intermittent horn issue? Do tell.

Is it intermittently not working, intermittently sounding when it shouldn't or .... ?

 

And this info may help, from the FSM - Integration relay (J/B is junction box IIRC) is your in-cab fuse box:

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My clock spring has partially failed causing my horn to work only when the steering wheel is turned from strait. Try turning your steering wheel while testing

 

On past vehicles, I've found contact cleaner on the grounding surface (if visible) can work wonders. Or if bare metal, and in a pinch, an eraser. Doesn't really apply for clock spring, but there is a horn grounding contact under the airbag.

OP, better hope it's not the clock spring, you don't wanna see what they cost. And it's NOT a part you want to skimp on, unless you really trust a low budget warehouse in China to make a product for dirt chip that's not gonna leave you eating an airbag, which may be the only other thing that costs more than a new clockspring

(if it comes to that, DO NOT buy your part on scAmazon, fleaBay or WallyWurld, risk of fakes is far too high!)

 

“Yeah so I smashed the glass, hot wire it and drive off and the horn is working intermittently, what do I do?”

 

For your MY 2000, the horn fuse is 20A not 10A.
I doubt it's both horns but if you wish to check, unplug horn and apply pos from battery to the horn connector pin.
Hopefully not but the Integration relay, located on back side of Fuse/Integration Relay, is part of equation.

From 2000 EWD....





The below video is a 2001 which should be sufficient for your 2000 if the problem is in steering wheel area. He has other good videos of interest.

 

I like the way this guy thinks, and the way he lays things out. Very well put together. This is essentially how I walk through diags, only I don't dig up the EWDs or FSM on most things. Very useful for this case.

I would've expected OP to mention airbag light or cruise not working. Hopefully it's also not another case of integration relay/fusebox taking on water from a windshield or a-pillar leak.

 

Thanks, It is intermittent and turning the wheel doesn't make any difference when it's being fussy

 

Cruise is fine, no airbag lights.

 

Isn't the ground on the steering wheel bearing(s) that require pulling the wheel?

thx

 

Is the relay on the back of the inside box? Pulls down or out?

thx

 

I just checked out that video, you can see it when he pops off the airbag, it's the single wire connected with a spade.

If nothing else is failing, that's the first thing I'd be checking, right after doing what Bubba suggested. Since you don't need to remove the wheel, it's easy enough to confirm the connector is intact. With only one thing related to the clock spring failing, I'm not convinced the whole damn thing is bad. Sounds fishy.

The fusebox itself is called the "Integration relay", and there are some relays on the rear, but I'd need to dig to find the purpose. These trucks have a reputation for windshield or A-pillar leaks pushing water into that integration relay, and this is what you get, pic also shows the guts of it, and here's another one from a different member which shows similar and also shows relays on the rear. But again, you'd be seeing other weird behavior (I personally think) if that were the case. A handful of people have fallen victim to this one. If you've ever had your windshield replaced or live in a place with salted roads, it could be what's happening. Or maybe you also have those relays on the rear, and one is for the horn.

 

I watched the video above. Does a bad clock spring always present with a bad cruise control and airbag light? Again, I only have the horn issue.

 

Main purpose of the clock spring is to take anything electronic on the steering wheel and allow the electrical contact pass it through on something that rotates in one or more circles. Things like: Steering wheel control, horn, cruise control, radio controls, etc. Some vehicles may even pass paddle shifters, blinkers and wipers through the clock spring.

Good way to think about it, if you were ever into BMX and/or freestlye back in the days, it's a similar concept to the Gyro brake system: You need a way to transmit an action through a rotational device (the handlebar). Gyro tech let you transmit brake via cable action thru a handlebar that'd spin around multiple rotations on a neck.

If you want to understand how it works, watch the following video. About 60% thru the video, you'll see the guts and how it works, and you can see towards the end a common example of how it breaks. In your case, you only appear to have one wired item not working: The horn. As you'll see in the video with the guts of the clockspring, The chances of only one conductor passing thru the clockspring being bad is pretty damn low. It's possible, but unlikely.

Now, with that said, as we know from the diagrams, you have one hot wire going from the rear of the fusebox/integration relay out to the driver side horn, and that piggybacks to the passenger side horn. If your driver's side horn was failing and not passing the signal, it could be at fault also (<-- this is wrong, see Bubba's comment below). Or if the integration relay wasn't passing through the signal that could be it. Or, as you see in the pictures I linked, if one of the relays on the rear of the integration relay is tied to horn, that could be it, but I don't they are. I can't recall the last time I've seen a dying relay that only intermittently sent a signal. Usually they fail-fail anyway, so ... doubt it.

https://www.youtube.com/watch?v=tI98pGCCFD4​

 

Great

As @shifty` alluded to, that whole box is your Integration Relay(IR)/Fuse Panel but the horn relay is part of the circuit board seen in pic below.

Couple of questions for you....

1) Since the 20A fuse protects the Horn, trailer socket and turn signal/hazard warning lights....do all 3 of those circuits work ?

2) Do you have a VOM(volt ohm meter) and you're able to check things ?
No disrespect....some folks don't like EWD diagrams and VOM is greek to them. Checking for voltage and continuity is a must on certain problems

Onward we go...the below pics might be considered overkill but it helped me understand your 00 compared to my 04 DC, which has an actual horn relay.

1....1 L connector pin 12 is gnd from horn switch for horn relay contained on IR circuit board
2....1 E connecctor(on backside of IR) pin 8 is the pos 12 vdc to horn once horn relay energizes, which is on front of IR on the circuit board(the horns are not in series, meaning if one horn breaks, the other horn still works)
3....pin 7 of IR is 12 vdc from Horn fuse

If it were me, before checking at horn switch of clock spring area, I would unplug the 1 L connector on front of IR(may have to remove Lower Finish Panel). I would place VOM on resistance, hook one lead of VOM to a GOOD gnd and the other lead to pin 12 of 1 L of the harness end. With that in place, attempt to blow horn. If that shows a short(horn switch works), we have to look further.
IF you have leads hooked up proper and you DON'T have a short, then the horn switch could be the culprit.

 

Good catch on this. Diagram makes it look like it's a series circuit. I was too lazy to go out and look at my own horn. I'll updated my comment above. Thanks for the correction!

 

First off, thanks for all the great expert help! I do have a nice Fluke and not afraid to use it I'm almost 75 so I need to digest the troubleshooting here but I'll give it a go. The panel below the fuses in the cab will reveal the rest of the IR? (Not on the back side)? Not sure why cruise would be related unless it was on the steering wheel (mine isn't; MY 2000) Thanks again

 

Yes, turn sigs and hazard work fine

 

"1....1 L connector pin 12 is gnd from horn switch for horn relay contained on IR circuit board
2....1 E connecctor(on backside of IR) pin 8 is the pos 12 vdc to horn once horn relay energizes, which is on front of IR on the circuit board(the horns are not in series, meaning if one horn breaks, the other horn still works)
3....pin 7 of IR is 12 vdc from Horn fuse

If it were me, before checking at horn switch of clock spring area, I would unplug the 1 L connector on front of IR(may have to remove Lower Finish Panel). I would place VOM on resistance, hook one lead of VOM to a GOOD gnd and the other lead to pin 12 of 1 L of the harness end. With that in place, attempt to blow horn. If that shows a short(horn switch works), we have to look further.
IF you have leads hooked up proper and you DON'T have a short, then the horn switch could be the culprit."

So, I'm only jumping the pin 12 of the removed plug to ground, nothing to do with pin 7 on the IR? Can I just use a patch cable or jumper or are we measuring OHMs also? Thanks again.

 

75 is nothing, your still a spring chicken

With a Fluke, you have more than enough lead length to find a bolt that is grounded in area of fuse panel even if you have to remove kick panel. Might have to take “Lower Finish Panel” off to see a good ground. It’s the panel you stick your hand thru to unplug the 1L connector.

With VOM on resistance, hook one lead to ground, touch other lead to 1L pin 12(should be green/red wire for your 00). Push horn and your meter should show short to gnd. This tells you if your horn switch is bad or corroded contacts of horn switch causing intermittent

The other choice is undo steering wheel airbag, flopped to the side and check the action of the horn switch.

Taking Integration Relay box out to check for possible problem is last resort IMHO

 

Battery disconnected for this test?

ty

 

Better safe than sorry, since I’m not the one checking

 

I wanted to add that when the horn does work, only certain parts of the wheel will trigger it; sometimes the middle, sometimes the lower left, etc if that helps?

 

Is there a horn "switch" that is not the same as the clock spring?

 

There is only 1 horn switch and as the guy mentions in the video posted in post # 7, the horn switch is inside of the clock spring.

If you'll view the video or re-view the video, starting at the 23:00 mark he starts talking about it. He also shows @ aprrox that point in time how to check if horn circuit works with clock spring removed. As mentioned before, the clock spring/horn switch supplies the gnd to the relay that then passes 12vdc to horns.

If you wish to do a similar test but further down the line from where he did. Cautiously apply a gnd to pin 12 of the 1 L connector of the IR relay box itself with batt hooked up.

All 1st Gen horn circuits are same. The below is from 2006 EWD and even mentions spiral cable, AKA clock spring(spiral cable)



From 06 FSM....

 

Based on the video, I'd say so, you clearly hear something clicking when he taps on the horn, but I don't know that it's a fancy switch like you may be thinking.

The symptom you added, "works in some areas and not in others" speaks to switch failure, especially when combined with nothing else on the clockspring failing.

I don't think your 2000 operates the same as my 2006, so I'd need to look more closely at videos of a 2000 to see how the switch operates.

 

Thanks for your patience, guys I'm in San Jose, Ca but always wanted to see the Big Apple

Still a little confused, I messaged the guy in the video and he said "NO", the switch is *not* the same as the clock spring. I will try the grounding tips when I get up the courage. If the switch (inside the air bag pad) IS bad, does the air bag assy have to be replaced? Thanks again.

 

Correct, that's what my reply said also. The three of us are saying the same thing

And to your question about the airbag, I'm not sure. You'd need to pop off the airbag to investigate (remove neg batt cable for 10 minutes prior, though, and don't reattach until airbag is reconnected!). If you have to replace the entire assembly that would suck!

This is the wire in question - it's basically a wire with female spade that connects to the airbag assembly. I assume the switch will be tied to that. Maybe that ground wire is just loose or frayed?

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Another shot:

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Clock spring going bad typically impacts more than one circuit that passes through the spring. This is why multiple wheel-function-items (like cruise, horn, wheel-mounted radio controls, etc) would be indicative of clock spring fail. But only one going bad? I doubt it's the clock spring. Add the symptom of "It only fails pushing on certain parts of the pad" and it lends to a bad horn switch.

Couple more shots of where the horn connects. I think where the wire connects is just a simple plate, that's not removable. I'm not sure if there's anything you can realistically do, diagnostics-wise with this thing. I assume the horn switch is embedded under the airbag cover, and I can't tell if it's removable.

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