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1997 Nissan Sentra cooling fan won’t come on

hey guys,

i’m having this cooling fans not coming on, even when a/c is turned on. i replaced temperature sensor, nothing. to make sure the sensor is working, i placed a ground on one side(input) and another to the next side (output) of sensor to the ground of the fan relay.
1.I started the car and allowed to to idle. the fan came on after a few minutes, which indicates sensor is ok. also did a resistance test in temperature rise and it’s responding to temperature change.
2. there’s 5v from the ecu, to the sensor. when removed, the engine races up, usually the fan suppose to come on at that time but doesn’t

is it possible the i have a faulty ground output from the ecu? did a continuity test on the ground from the ecu, it’s not broken.