So... I just replaced the radiator fan because the low speed didn't work. After I put it in I tested it with the obd1 and both speeds worked. Took it for a rest drive and the low speed didn't come on, but high speed did. Any ideas?
Since you were able to turn low on with the scan tool, that leads me to believe the IRCM, fan motor & associated wiring is good & that the ecm is able to control the relay's in the IRCM. Possibly ecm is not getting correct signal from coolant temp sensor? Does the your A/C system still work & does the low speed come on with it? Do you know what temp the high speed is coming on at-low speed temp 195? or high speed 210?