So….when the headlights are off, the headlight circuit would open……yes? Cranking the engine wouldn't matter. But if the headlight circuit is shorted to the starter wire ….somehow…..then when you engage the starter it would shoost high current through the headlight circuit. (as Lisa on Green Acres would say)

I see a trip to the wreckers coming up …

Well, Mr. O. A good detective always works better if he gets a clue. Anyway, thanks for sharing! Stay healthy!

yeah jerk, hold the little bight yellow car hostage for not having crappy headlights on during the damm day

Very, very interesting case here. Great job diagnosing this weird issue.

The one question that keeps lingering for me is, what happens when the ignition switch is in START that doesn't happen with ignition switch in any other position (if Low Beams are on, but not when they are off), as it relates to the Daytime Running Lights module?

It appears that the load side of the relays, Pin 30, connects directly to the battery and the fuse is in the leg from the Relay Pin 87 to whatever load there is. This seems to be true of all, or most all, the relays. Obviously, the Starter is engaged through the Starter Relay. And, we know that the Starter draws a lot of current. Because the view was of the Meter each time Eric cranked the car, I could not see if the headlights (low beam) dimmed or not, and if so how much. Now I know one test had the left headlight disconnected, so that cut the normal current down in about half, so it would not be the headlights themselves, as this test pretty much proved.

I wish we could have seen the battery voltage when cranking both with and without the Low Beams on. I ask this, again, because there is something that happens when the ignition switch is in START that doesn't happen when it is in any other position, which causes this issue (only if Low Beams are on). Since Pin 30 (load side input) of both the Starter Relay and the DRLs FET (Field Effect Transistor) power input connect directly to the battery (FET through fuses – EF1 in Engine Compartment Fuse Box, and F15 in the I/P Fuse Box), the main thing that does change is the battery voltage will drop when ignition is in START..This is normal, but should not drop to below about 10 volts.

The DRL Module in the I/P Fuse Box might just be bad. Or, something (an input) to this module happens when starting and Low Beams are on into this module. The one thing I can think of is the battery voltage dropping enough to switch the DRL FET on (grounding the LTGRN/BLK wire, which would cause a direct short to the positive side of the battery, IF, the Low Beams are on, across fuse EF21 in the Under Hood Fuse Box, the one that is blowing). This would not happen when Low Beams are off, because relay HDLP LOW RELAY in the Under Hood Fuse Box is not on.

Finally, even if something like I have described (battery voltage dropping, or something else into the DRL Module) is happening, it probably should not cause the DRL FET to drive the LtGRN/BLK wire low if the Low Beams are on. This should never happen under any condition. Since this same module controls turning on the Low Beams and High Beams, as well as Fog lights, through the Headlight Switch & Fog Light Switch, it appears to be working except for the DRL part. I wonder if the Headlights are turned off (or suppose to be, to extend battery life), by this module, when cranking (ignition in START position).

As stated, very interesting. One of the most interesting ones, and extremely well done diagnosis that Eric did. Impressive. And, thanks Eric for taking the time to make this video. It is appreciated very much.
Omegaman

Great diagnosis on this electrical problem. You are a talented self-made mechanic/technician. I enjoy watching your channel.

Had an old neighbor ask for help changing a fuel pump on an early 90s chevy 3500. Said he had a used pump, the pump was in a tank that he said came from a mid 2000s silverado. Told the guy there's no way the pump would go into the old tank. He cut the harness off his truck and wired up the newer pump but left it in the newer tank so it was in no way, shape or form made to fit under this truck properly. The guy stuck an exhaust adapter in the fill hole on the tank to be able to attach the fill hose and wrapped an old rope, like the ones you had to climb In school around the tank and frame several times to secure it. Trust me, there's much more on the roads to worry about than this guys headlights. Needless to say, if I ever seen the guy on the road after that, I went the opposite direction.

This was a great video Eric and I hope you didn't charge this man for the diag, the experience and seeing such an odd failure is worth the time spent.

Sweden is one of the countries where Day running lights DRL are required by law (since the early 70's)

I've seen a couple of those Aveos with a DRL module that has caught fire. I'm wondering now if it was because someone jammed in a higher amp fuse

Half way through I made some popcorn and then enjoyed the resolution. Thanks Eric!

Eric,, Amen brother glad you understand freedom kudos to you.

"… welcome to the real world kid…". Wish more ppl understood that!

Hiya Eric

Damn, I wish I could get my vehicle to you. Maybe you could tell me why my 99 Toyota 4Runner won’t engage the AC compressor clutch at idle, only when the gas pedal is pressed.
It’s driving me nuts.

definiteiy one of best diagnosis you have ever posted.

Good future reference video Eric.Thanks for the lesson.

"Hypothesis 478" 🤣😂🤣 I about died.

I have that same amp clamp. It does not have an auto off function. If you leave it on, it drains the battery. I keep spare batteries in the drawer with it.

To no avail it's still not fixed!!

WOW! . . . and you're not an electronics guy! Yeah, right. GREAT JOB!

Not a big electronics guy??? if you're not, the rest of us are doomed!