I've been analyzing the drl circuit on 2nd gen and read pretty much everything there is in the forums.
we know the body ecu drl pin is connected to the 12pin flasher relay and that controls the drl.
mods abound about cutting that line and adding switch to enable/disable the drl function. What I have not found is an explanation on how the drl works. The mods are simply trying out a theory and it works, without really understanding why.
The only post I found that questions how drl works is this one
but nobody really gave any good answer.
same as that post, I checked the drl line with a voltmeter, and it has no signal at all, regardless if parking brake is on or off, headlight is on or off. So I have the same question as that post, if there is no signal, how does the relay know when to turn drl on or off???
I verified it is not a ground circuit. connecting one side of relay coil to +12 and the other end to the drl line does nothing.
The only possible explanation left that I can think of is that line puts out a pulse to signal the relay.
my objective for trying to find out how the drl line works is so I can use it to add drl without having to use the 12 pin flasher relay.
I know there are several drl mods out there that does not use the 12pin flasher relay, but I want one that works like the oem drl, that is, drl is off if parking brake is on or headlights are on or turn signals are on, or hazards are on.
perhaps someone with service manual or alldata can find out if there is any info about the drl. any useful info regarding how drl line works is appreciated.