Hi, I just purchased a 2003 4Runner as a fuel efficient alternative to my 100 series. 
The car previously had an ecm failure and is now not running due to the second ecm failure. I have pulled apart the new as of a couple months ecm and one of the microcontrollers is burned. I verified that the battery is good, relays are good, starter was recently replaced, no obvious grounding issues, and the ecm is receiving power. I will replace the ecm but want to find the issue before I burn out a third one.
History: The car has had ecm and bcm replaced by dealer once. Two months later, the previous owner went to the dealer because the dome lights would not turn off and they replaced the bcm and then the ecm died.
Currently: The car cranks in every position of the key but will not start. The immobilizer has been verified to not be the problem. Found there is engine speed input to the ecm, and STAR terminal sends power to start even when not in the start position and it is not the park neutral switch. I have visually checked coils, oxygen sensors, injectors but will probably test or replace them.
Future: I will replace the ecm. I figure the ecm may not be protected from continuous overvoltage so I may change the alternator to be safe. There seems to be no obvious shorts that either me or the dealer could pinpoint and I would guess that the ecm would be protected from most shorts. I am curious what parts of the ecm would not be protected and could cause it to fail? Wondering if it could be a can bus over-voltage by touching the 12V. Would anyone know whether this specific microcontroller is for the bus? Otherwise, what else could keep causing ecm failure?
I will be very appreciative for help, honestly if anyone helps me figure it out I will venmo 100 bucks.
The car previously had an ecm failure and is now not running due to the second ecm failure. I have pulled apart the new as of a couple months ecm and one of the microcontrollers is burned. I verified that the battery is good, relays are good, starter was recently replaced, no obvious grounding issues, and the ecm is receiving power. I will replace the ecm but want to find the issue before I burn out a third one.
History: The car has had ecm and bcm replaced by dealer once. Two months later, the previous owner went to the dealer because the dome lights would not turn off and they replaced the bcm and then the ecm died.
Currently: The car cranks in every position of the key but will not start. The immobilizer has been verified to not be the problem. Found there is engine speed input to the ecm, and STAR terminal sends power to start even when not in the start position and it is not the park neutral switch. I have visually checked coils, oxygen sensors, injectors but will probably test or replace them.
Future: I will replace the ecm. I figure the ecm may not be protected from continuous overvoltage so I may change the alternator to be safe. There seems to be no obvious shorts that either me or the dealer could pinpoint and I would guess that the ecm would be protected from most shorts. I am curious what parts of the ecm would not be protected and could cause it to fail? Wondering if it could be a can bus over-voltage by touching the 12V. Would anyone know whether this specific microcontroller is for the bus? Otherwise, what else could keep causing ecm failure?
I will be very appreciative for help, honestly if anyone helps me figure it out I will venmo 100 bucks.
