While off roading in my 1990 4Runner 3.0 the CEL started intermittently coming on, stayed on a few seconds then would go off. Drivability was normal. Then when coming to a stop, it stalled, would start was rough but not stay running. gave code 24 & 42. The next morning when when checking things, it cleared up. Drove it a couple miles in dirt and CEL started flashing again. Cleared codes and drove on highway, no issues. Drove 130 miles home and all was good.Since it failed while off road, my guess is something loose or breaking. Did not find anything physical. Getting multiple codes from different areas leads me down the ECU road. Anyone have similar issue? Not sure how to diagnose at home if I cannot get it to fail

 

Do you have the list of Toyota Diagnostic codes tattoo'd on your arm? Neither does anyone else. So if you just throw out a number, you're limiting your potential responses to those from the savants who, for some reason, have memorized all the codes. YOU know what the codes mean (don't you?); just say it.

Unlike codes for, oh, Lean malfunction (25), both 24 and 42 point directly to a single sensor (and its wiring) (air intake temp and speed sensor). You say you did not find anything physical, well, that all depends on where you looked. I'd suggest you start with looking in the right place. If that doesn't help, just run the FSM diagnostics on the sensor, then move back to the ECM connector and check electrical from there. If the problem is intermittent, you might need an assistant to do the "wiggling."

FWIW, it is VERY unlikely to be the ECM.

 

Thanks for the reply and the laugh. Didn't notice that I left out some obvious things to make getting help easier. FSM flowchart is my plan when I can get it to fail. Tried simulating speed and rpms that I was driving while my son bounced around the ECU a bit, but unable to duplicate. Might just have to take the FSM with me to the desert. One thing that threw me off was the light. It would come on for about 3-5 seconds then go off. A few miles later the same thing. I know OBD I is pretty simple, but I have never had a light go off and on like that.