I have an 08 TL with the nav traffic system. Near as I can tell the output from the HU to the amp is NOT crossed over and is full range to all 5 channels. The sub channel out of the HU doesn't look crossed over either. Can anyone confirm?

 

Yes, no crossovers but no, not full range - the HU itself does EQ and other wave shaping to optimize the stock speakers. The output from the stock HU is not a flat graph. There are some threads about the output from the HU.

Note there is a simple cap on the tweeters for a highpass filter.

 

To add to that, the factory sub does not run full range either.