2004 chevy aveo that the check engine light keeps coming on. The electronic find showed three code PO 128, PO 700, and P 1781

P0128 - the thermostat may be stuck open or has anyone put a colder thermostat in the car,because once it starts to get cold it will throw a SES with a colder then stock thermostat. Replace the Thermostat should fix this problem.

PO700 is a code telling you there are codes in the TCM of some late model cars where the Transmission control module has been removed from the PCM the vehicles main computer , and basically it happens when the TCM has a issue within itself or the transmission that sets a code and it sends a request for the PCM to illuminate the SES or CHECK engine light. To get at the TCM codes requires in most cases the most up to date scanner software purchased after the cars model year and as of yet is still a little iffy. Standard OBD11 scanners will generally not be able to see these codes.

P1781 is set during engine start up when the ECM & TCM do not communicate properly during initial power up. It will only illuminate the service light if the condition occurs in 2 consecutive start cycles, but the DTC will be stored in the failure records after the first cycle.

Replace the Thermostat and go to a transmission shop that can read the DTC codes with a scanner and reset the ECM for clear the codes. Most Transmission shop will do that free of charge, if not turn the Ignition key's to the on position and and pull the ECM fuse out for 30 seconds and then place it back in. Turn the ignition keys to the off position for 10 seconds and then start the car, the engine may stall but let it. Just start the engine again, the ECM is just relearning the engine and go for a test drive. This will clear all the DTC history in the ECM like the day it cam off the assembly line. Good luck and keep me posted, be glad to answer ay more question.