the amm code wil not affect the ect code or vice-versa. the only common denominator is just the ecu. the ect code in the trans may keep it out of overdrive.

do this, pull the fuse to both ecus and leave out for about 15 minutes. the clears the codes and resets the adaptaion. install and drive. doesn't come on right away-nothing major but still needs checking. if 1 or both sensors is only a little out of whack, the adaptaion will cover for it until it runs out of adjustment.

on the amm, peel the boot of the connector, so you can see the backs of the terminals. use a digital meter and measure your battery voltage. pull the connector of the amm, turn the key on and look for battery voltage on the blue/yellow wire and battery ground. key off, plug it back on, key on. poke the blue/white wire and look for 1.4 volts. ok, start car and check for 2.4 volts, raise rpm to 3500 and check for 3.1 volts. all ok, let it go. any variation from spec is a bad amm.

on the ect, peel the boot. i think you need the gray/white wire for this. key off, unplug it, key on. look for 5, not 12, 5 volts on that wire and battery ground. key off, plug it in, key on. poke the same wire. depending on the temp of the engine, the meter will read between 2.5 to 3.5/32f to .5 or less, fully hot/190f. any minor variation may be due to temp, anything major check the resistance of the sensor, 6000 at 32f, 300 at 195f.

check all the connectors for corrosion and follow the wires back to the bulk connectors, also. clean and tight.

121 usually is automatic for amm replacement, 123 could be either the sw or the connections elsewhere. the test for 123 assumes the thermostat is working and the engine can reach operating temp. 123 sets when the ecu gets either lower than -40f or higher than 240f. good luck, chuck.