Well, mine is a special case, because I had to make my system work with a non cruise control clock spring, AND I didn't want to alter the existing green connector coming from my good steering wheel switches, and so I had to modify two solderless push on connectors to try to get them to slip tightly over the two pins on that green connector, and I think that I just did a crappy job of it the first time around, which allowed them to rattle around and make very brief disconnections in the circuit at random times, and as soon as the total open circuit time added up to greater than 3 seconds, the PCM then decided that it wasn't going to allow me to turn on the CRUISE light again until I restarted the engine.
And of course with me previously not knowing about this PCM behavior, I was monitoring the voltage on the speed control signal pin of the PCM while I was driving the vehicle, and I couldn't figure out why the cruise control was behaving like it was when the monitored voltage always seemed exactly perfect. The correct voltage for that pin, when the 19.5K ohm switches are connected, is about 4.7 volts with no buttons pushed, and a little over 5 volts open circuit (with no 19.5K ohm present). But I would have needed a recording oscilloscope or something like that to have been able to see the brief voltage changes that were occurring without my knowledge. It never occurred to me that the PCM would for some reason add up the total of all brief open circuit conditions and then shut down the system once it had collected 3 seconds worth of them. I'm relatively new to computer managed vehicles, and so I'm not used to a vehicle failing due to something that happened in the past and is not currently happening anymore. What's next?... The PCM deciding that I've had too many flat tires this year and so it shuts down the vehicle until I get new tires?
Until I have driven the vehicle for a month or so after improving my green connector connections, I won't be able to actually say with 100% certainty what was causing my intermittent open circuit conditions, and in fact I can't even say that that was my problem with 100% certainty, because it is also remotely possible that there is some other sensor or condition that is not satisfying the PCM and causing it to do similar behavior.
But regardless of what the situation is with my particular vehicle, everything I have said about this PCM behavior is true, because I created resistances to stimulate the 19.5 k with no buttons pushed and 440 ohms with the cruise control on off button momentarily pressed, and connected them in place of the existing steering wheel switches, and was able to repeatedly get the PCM to exhibit the behavior that I described. Whenever I disconnected the 19.5 K ohm fixed resistance for a total time of greater than 3 seconds, no matter how brief the interruptions or how many, and no matter whether the cruise light was on or off while I was doing this, the PCM would exhibit the behavior and I would have to restart the engine to get the PCM to allow the cruise light to come on.
I will report back in a week and a month how my vehicle is doing, but in the meantime at least now it's recorded how the PCM behaves, so that people won't pull their hair out trying to figure out why a system that tests absolutely perfectly still won't work right because the PCM has decided that there has been greater than three seconds worth of open circuit conditions since the last engine start and so the PCM then shuts down the system until you restart it.
My OBD2 reader did not read any error codes during this whole process, but I can't say with 100% certainty that there is no code for "speed control signal - (history of) open circuit conditions"...if so, that might have saved me some time on this project.
I will recreate the problem and then check with my code reader to verify that there is no code generated, or there is.