The ES 300 has some self diagnostics built into the microprocessor to help in troubleshooting the system.
When a failure occurs one of three codes will appear in all the display windows; F1, F3 and F9. F1 code:
An F1 indicates a malfunction in the control itself, and the control should be replaced.
Overheating kenmores have been known to give an f1 due to a faulty sensor or frayed wiring. Even if the sensor has proper ohm readings at room temp, it could fail or a frayed sensor wire could malfunction at high temps. It may well be the board but since you changed it out before, you may consider checking sensor connection and getting a new sensor from repairclinic. Send it back if it doesn't solve the problem. Also since the ecm is becoming obsolete, you have some figurin' to do..... ie it's kenny time..... l
Edited by DurhamAppliance, 19 December 2012 - 10:55 PM.
It's worth testing the sensor resistance at one or, prefereably, two other temperatures. You should monitor the oven temperature using a K-type thermocouple (either a stand-alone instrument or as one of the built-in functions on better multi-meters) and then measure the sensor resistance at the sensor harness on the ERC.