test light led

the only reason i can see the use of an led test light would be checking pulsing circuits like stated above but from my experiences id rather use incandescent test light because the bulb will put a load on the system. Were a led uses much less voltage to light that being said led may tell you you have voltage but does not tell you if your having a voltage drop issue and might lead you down the wrong path for diaq

Depends on what one's checking, I would expect.

I would agree with you that often the higher current for the incandescent light may indicate a problem where the LED may not have the draw to indicate a voltage drop issue, but some electronics circuits may actually be damaged by the higher current.

Not sure if you are referring to one of the videos or what but there is likely some missing context. I assume it was probably recommended in the context of general efi diagnostics. I cant think of too many situations in EFI where an incandescent lamp is going to be preferred over an LED. You can always leave the circuit loaded if you think there is a weak connection but there are probably better tools than a test light for that.

As tuners we are typically not there to fix a headlamp switch, more typically with EFI diagnostics, the first step is a quick test to verify if a signal is present or not.

If you want to see a 2ms pulse to check an ignition drive or injector output is working, then an incandescent lamp isn't fast enough, but an LED will show it fine. If you want to check a crank signal is reaching the ecu then an incandescent test lamp is not going to work either due to the current requirement, again an LED will do it fine. If you want to check a temp input pull-up is present, then again an incandescent wont show it but an LED will...