Rear defogger does not function

The rear defogger switch pins description.

The following has been well tested with the 2 connectors detached from the BCM unit.

1. Shows continuity when rear defogger switch is pressed.
2. Relay clicks when corresponding relay wire of the output connector is grounded and led lights come on.
3. All fuses relating to this defogger are okay and others too.

However, with all connectors attached back to the BCM, same process is check but no relay clicks, no led lights and eventually no defogging!

Earlier, when switch is pressed and released, relay clicks and led comes on. Again, when pressed and released again, defogger is off.

Please help. Thanks.