No head/tail lights or turn signals, squirrel chewed ground at J4

Testing pin side (male) of IJ1:
grounding pin 9 = ECU clicks, low beams with stalk set to high.
10 = something up front clicks, DIM or HEAD relay? no lights.
9 and 10 together = both things click, only low beams with stalk set to high.
pretty sure it's the low beams anyway.

Also, DIM stops buzzing when IJ1 is disconnected.

 

Just a thought here but did we verify the high beam bulbs are even good? Doesn't explain the buzzing relay but would explain no high beams.

 

Pink (Headlight) and Red/Green (High Beam) or Red/White & Red/Green at the same time for the Body ECU to activate the High Beams

And neither of those combos light high, but now I've lost it, I think one did nothing, the other did low. I should write this down when I do it.

 

How do I check those? Kind of weird if they both died at the exact same time. They are LED, would that cause a problem?

 

I think I tried cross-grounding pink/r+w with IJ1 connected, the ones in italics at the switch, and pink+r/g at ECU, no high beams. But just noticed the r+w at IJ1 is for flashers, didn't try it with flashers.

 

Pull both the HEAD and DIM relays and jump Pins 3 & 5 (larger terminals) in both relay sockets, High beams should come on if the bulbs are good.

I've seen it before multiple times where both headlights were failed.

They could, there's decent ones and others that have downright terrible circuitry.

 

Bulbs are good. They did look a bit dim, but that's probably because it's sunny.
Or would using 5 max amp wires to jump the sockets limit the power?

 

Now the DIM relay has stopped buzzing, it did that once before. Also, wiggling the DIM with HEAD removed makes the parking lights flash, but doesn't with HEAD in.

Neither of these relays are making sense to me.

With both test light and digital tester-
HEAD shows power on pins 2, 5 *and* 1/ground, however it only shows power at 1 on the digital. The light on the regular one stays dark on pin 1, but digi shows 2.71V. I think the test light is 5V minimum?
Digi also shows 12V at pins 2 and 5. Neither tester changes at any stalk or switch setting, except with the key off, digi stops showing 2.71V power at 1/ground.
HEAD shows no ground whatsoever with either tester.

DIM slots with HEAD in, switch on, stalk forward show power at pin 2/ground, and show ground at pins 4 and 5.
The test light lights up on 2 only when testing for power, and lights up on 4 and 5 only for ground.
Digital to (+) battery shows (-)12V on 4 and 5, and to (-) battery shows (+)9.7V on 2.
Furthermore, test light from (-) battery to DIM pin 2 turns the parking lights on with that 9.7V!

Also, the DIM is now buzzing weakly when wiggled around when loose, but has gone from buzzing constantly with high beams on to being silent with HB on.
What the heck?

And yes, I noticed the wires I used to jump the relay pins to get the high beams on are too small for sure when they started smoking after 20 seconds. So yes, they are a bit dim now that it is dark out, but I guess that is due to the under gauge wires that are rated for 5 amps DC.

One more random thing, the turn signals were working, but only with headlight switch on and stalk forward, but they stopped, no idea if that would be related to the buzzing.
Is there a turn signal relay?

 

Does your truck have Daytime Running Lights?

 

No need to mess with the relays.
We know we have a control issue via the pink wire.
Let's tackle one issue at a time.

I propose we leave the IJ1 connected.
Then use a back probe on the pink wire, and pull the probe down to ground with a test light.
Doing it this way, leaves the circuit for the dimmer intact.

If the headlights come on, push the stalk forward and see if the high beams come on.

BUT....Let's wait for @Dm93 to see if this is a viable option.
If so, We will explain how to back probe later.

 

No.

I really don't get how those tester results align with this diagram.
+12V at 2 and 5 at HEAD makes sense, but where does the 2.71V at pin 1 come from, the ECU?

And DIM shows nothing with HEAD removed, but plug HEAD in and DIM has 9.7V of power coming from the ECU(?) on pin 2, and the headlights (4,5) are grounded?
But...2,4 and 5 DIM slots aren't connected to HEAD?

1 and 3 DIM slots, which are connected to HEAD, show nothing.
Huh?

 

Still trying to wrap my mind around this.
Can the control issue be described as "the ECU is splitting ~12V of power unequally between HEAD pin 1 and DIM pin 2, instead of grounding them"?
Or...the pink wire is shorting out somewhere between switch, IJ1, and ECU?

 

Think of it like this.

The ECU sends 12v down the pink wire.
As long as the pink wire never touches ground, it stays at 12v.
And the headlights stay off.

If the pink wire touches Ground, the ECM see a drop in voltage.

When it see this drop in voltage. It send a signal to the Head Relay, turning the head lights on.
That “signal”, is actually just the ground for the Head Relay.

Also, the voltage can be anything the manufacturer wants.
It doesn’t have to be 12v.
It can be any voltage the manufacturer sets it at.
Most often it’s 12v, or 5v.

 

What about this? Would it explain the no ground at HEAD pin 1?

IA1 pin 29 White wire Headlight Relay Control from Body ECU (B5 Pin 14) to HEAD Relay Pin 1

Wait, did I already test that?
Edit, yep but probably not correctly. Will try that again.

 

Yes. That would explain why you had no ground to pin 1.
The ECM was not providing the ground.
(And it won’t until the pink wire is grounded)

 

Srry for the late replies, busy day at work and had a class on EVAP systems after work.
Just getting back to this so looks like I'll have to try to catch up.

 

After reading all that really the only thing that makes sense to me is we either have a bad ground somewhere, corrosion/meltage in a connector, or some wiring harness damage somewhere. We should not be seeing stray voltage on Pin 1 of the HEAD Relay or Pin 2 of the DIM Relay with the relays removed and going from Battery - to Pin 2 of the DIM relay certainly shouldn't cause the Body ECU to turn the TAIL Relay on.

Did we ever check that 1H Pin 18 (White/Black) has a good Ground?


Have we voltage drop checked the main grounds on the truck?
Battery Negative post to:

Engine Block
Body
Frame

 

I don't believe we have.
But some where in this 6 pages worth of diag, I believe that wiggling a relay makes the turn signals come on.

I'm going to have to go back and read all 6 pages worth.
Maybe we missed some key info......

 

Don't forget the squirrel, one may have nibbled on a wire somewhere hard to see, it was trapped in the cab overnight , chewed up the passenger door window sill and back seat foam under window trying to escape, luckily this is a farm truck.
A squirrel did chew thru the brake fluid low sensor by engine, it's still cut, but that was before the headlight problem.

Will test all those other points soon.
Side note, those mouse repellent packets that smell like patchouli seem to repel squirrels too.

 

Wait this is new information, I don't recall reading anything about a squirrel in this tale.