Not primary purpose. Pin 5 is a simple on/off switched pin. If it has 5 volts it runs, no 5 volts it is off.
I had played with a similar design from my "tracker" days.
Ever installed a CB in one of types of SUVs'? Then you'd know they (Gosh Darn GM's) emit a lot of "buzz" that NB and ANL won't take out. Even the Vehicles own AM stations were drowned out by this noise. It's a local sourcing noise abatement problem - you show the circuit it in the nearly EXACT design the Tracker uses in their DRLS, Nighttime and Wiper control system. Nearly identical in function alone - mine used 6-gate (Octal)
Only thing that is missing in your schematic is it's CAN-BUS communication - that is what that controller was for - to light up the Maintenance or MIL light to tell you something's wrong and set a DTC so you can see it with a scanner. The controller "polled" the NPN inputs and if anything went flat or out of range - sent error codes to the main PCM - which then set the flags and - if needed - the MIL light on the dash. Else the controller simply sent pulse trains - like shown above - and if the polling something strange to the controller - the thing would cycle - you'd hear it thru the CB - almost like the older technique of radar detection - their generated noise would grind in on the normal background noise of the CB channels' you'd listen to while driving. Easily subjected to vibration and can knock out the CB radios' receive while it was doing it's stuff - until - "Blink" the "Check Engine" light comes on...
Canadians had (still) this circuit installed - not sure of now, but back then, it used a micro controller on a 4MHz Xtal and a "74xx" series AND controller. The inputs from the various systems it "follows" are buffered by NPN and the device emits the noise due to the harmonics the square waves pulse train used to generate.
Had to track down the device and remove it from the vehicle - took away the DRLS and all the other convenience stuff but it was "transparent" so it didn't hurt the performance - you just had to remember, it won',t so, you do - in controlling the thing.
Some things are nice and novel - and the unit used MOSFET driver for the lamps which ran about 56-60% down from full current - but Trackers aren't "smoothly riding Cadillac's" - they bounced and rattled like any other SUV from that time and they blew bulbs from the vibrations - so you still had to run around with a glovebox full of spare fuses and even wires in case anything from the taillights on up burnt out while on road of off.
So yes, your idea may not have been it's initial intent - but that "snippet" of a driver circuit has been used elsewhere. I had direct experience with one of the offshoots of this design, fun days...
So, that's my take on it...used to check and reflect status....
It operated in a Truth Table function.
Engine running=ON, Brake = OFF , Nite Minder = OFF, Wipers = OFF - then equated to DRLS = ON
Engine Running=ON, Brake = ON. Nite Minder = ON, Wipers = OFF - Brake superceded Nite Minder DRLS = OFF
Engine Running=ON, Brake = OFF, Nite Minder = OFF, Wipers = ON - then DRLS OFF - LIGHT = ON
Just some examples...
So you kinda had a "logic tree" of events in which to set the condition - that device helps to display the condition. The inputs then selected by priority - the condition - expressed by DRLS or Nighttime driving mode...
Saturns' even used this...
