I have had problems with my auto wipers - they only work if you tap on the sensor. Yesterday I was in the parking lot trying to see if I could get them to work consistently. I removed the plug going into the sensor and now I have intermittent wipers. The minus is about a 12 second delay and the plus is a four second delay. I have not heard of this, so I thought I would pass it along

 

ok this is something even I havent heard of a delayed function, anyway what you could do is disconnect the connnector from the rain sensor. In the Engine Bay remove the FR - WIP WSH fuse and IG1 fuse, Wait for 5mts and reconnect the fuse. Connect the harness connector to the rain sensor. Check the toggle s/w below your steering wheel of the Wiper switch. Do not twist to Auto mode, Ensure it to "LO" mode. Now insert the ignition key to "ON" and test it, It should be fine, otherwise, you need to buy the sensor tape, here is a sample, I have the same problem, not exactly the delayed response, but only when the sensor case was pressed harder towards the windscreen it would work. I picked up this from Magnussen for 20 bucks. Maybe you could try this, if it still does not succeed then it could be sensor harness.

 

The intermittent wipers is a result of disconnecting the harness from the rain sensor. Once I disconnected it, the intermittent function started working when the switch was in the "Auto" mode. I was just trying to pass the information along. At some point, I will try work on getting the auto to work properly.

 

You need the erase from the ECM memory, just follow the instructions as the erratic function would cease after the removal of fuse and refit.
Ensure the Battery terminal is removed ( Negative ) prior to the start.

 

Don’t know why but werx 4 me too!
2007 GX-470