So for a good while now, my 4runner will not start from time to time. There are days when I can start it up just fine and drive it without problems but when I turn it off, and turn it back on at the worst time it has to tendency to not start, only click. It doesnt do this EVERYTIME but rarely it does it and it seems to do it at the worst possible time. When I check for codes it only gives me engine code 12 when it decides to not engage the starter. HOWEVER, when I disconnect the battery, reset the codes and the ECU, of course it doesnt show engine code 12 anymore because I resetted it, but when I turn the ignition on after resetting it engages the starter to start like nothing happend. I also have a new starter on because I thought that was the issue with the old one but no. And its not the distributor either because I replaced the whole thing too. It just does not wanna engage the starter and you can hear it click.

1991 Toyota 4runner
Engine: 3vze
Manual Transmission

 

The code is not related to the stater not engaging. The ECU has nothing to do with the starter signal, it receives a start signal from the key, but that just tells the ecu to use the base timing while cranking.
It sounds like your starter contacts are worn and that gives you the hard single click noise when the starter gets hot. If its a rapid click you need to check the battery and alternator. They ignition switch can also cause the single click if it is worn or corroded.