No Red Light on Fixed 1

Check and see if there's an internal short directly across that channel.  The TVS protection diode may have shorted and is keeping it from working. 

Try an aux power supply to see if the thing will turn on. A Lionel command base wall adaptor  will work for testing but not quite enough ummmph to use  regularly.

Any wall wart of 12-18 volts will work for testing, but may not have enough power if there's a string of AIUs.

Check to see if you are getting voltage to FIXED 1 input.

Are the Z4000 A & D posts connected directly to the TIU inputs?  IS there a Z4k receiver in the mix?  Have you switched the outputs from A & D?  I'm trying to pijn down whether it's TIU, Z4000, or wires between them.

Are you attempting to use only Fixed #2? If so, the TIU will not power on and the red LED will be off, even though power passes through Fixed #2.

In order for the TIU to work on any channel, there must be power into either the Aux. Power port or Fixed #1 In.

Yes, fix 2 was working with auxiliary power but why was it working with out auxiliary power and fix 2 was the only one used? The Z-4000 was supplying power to the TIU. That is what's bugging me now. Also, there was no additional devices connected to the Z-4000. The Z-4000 is supplying power to two circuits but only one has DCS at the moment.  Thank you everyone for the advice to fix the problem.

but why was it working with out auxiliary power and fix 2 was the only one used? The Z-4000 was supplying power to the TIU.

That isn't simply possible with a TIU that's properly functioning with proper wiring. Period.

Either the TIU is defective or there's power back-feeding Fixed #1 Out.

Fixed 2 is a straight through connection, whatever goes  in comes out the other side, however  as mentioned the tiu need a power supply to turn on (operate... function) and that is power to fixed 1 or an aux power supply. Did the red led light up  on top of the tiu? it's not exactly on top  but you'll find it. No dcs signal if the tiu is not turned on.

Gentlemen,

    This is why I recommend always powering the TIU thru the Aux port, it eliminates any one thinking they can power the TIU thru Fixed #2.  Use a RS 24/18 power pack or some other transformer to power your TIU thru the Aux port, and eliminate all the set up problems.  There are also other running advantages to doing so, frees up another channel for running trains and the full emergency shut down works properly in this manner.

PCRR/Dave