Charles,
Before chasing the shuttle, Can you please confirm that the sensor itself is operational.
On the "S88 Configuration" panel you should dynamically see the state of a sensor change.

The squares are normally clear, when the loco or you manually activate them they become dark as in Peter snapshot.

Hi Yes you are right clear . I have 2 S88 both 16 ports when you are in S 88 configuration the first one looks like the picture but it is the last box that is clear if you turn the red control knob to the second one all the squares are black. I am using ports 1/2 on both of the S88. I hope this makes sence.

Hi: I have not played with my S88 for a while, but I did have a shuttle train set up this Xmas, and one thing that I always checked was whether the boxes you circled above filled in when I ran something over the detection track. If that works, and you can dynamically check that in the CS screen you have depicted above. If you cannot, then you cannot expect the shuttle train to do anything but what you are seeing. I would consider swapping the inputs to the S88, possibly doing a test with just a single module, and then building up to where you want to be. Like many technical things when they work out of the box you are golden, otherwise, one must carefully backtrack and test, test, test!!!--MM

Hej Charles.

You may already have seen this topic where my s88 problem was solved by help from members, but here it is anyway:

https://www.marklin-users.net/fo...ault.aspx?g=posts&t=9107

There are a couple of important steps: grounding of the first s88 and ownership deligation.

Good luck with further investigation.

Simple Test.

With the "s88 configuration" displayed short a wire between the T terminal of the s88 and any/all the numbered sensor inputs.

If the the matching block on the display changes from clear to filled then the s88 is working and your issue is out on the layout.

If you never see a filled in block then check your s88 to CS wiring

Charles, just to make sure, you are pressing the Stop button at lower left and not one of the big red knobs? I remember making that error, when I set mine up.

Ehh... I seem to have lost understanding of what you are asking. I can't really tell you much because my layout is packed away now and I can't remember the Shuttle setup by heart, but as suggsted by Michael earlier - make the simplest setup possible separated from your main layout. As for the s88 Configuration screen (Peters picture above) Module 1 is selected ("cursor" turning the line black) and port 5 (red circled) is activated - shown as a white square. If a running loco is activating port 5 you will hardly notice the short change of state, so in order to take this photo, Peter has parked the loco on the circuit/contact track to keep the changed state. For the unselected module 2 the colour scheme is just the opposite. If say port 1 of module 2 was connected and activated (assuming module 1 still selected) the outmost right hand square would turn black - either as a blip or a constant change depending of how you activate it. Port numbers are counted from right to left. Hope this helps a bit.

Hej Charles,

So you have a change of behaviour from that of the beginning. Just to understand it correctly: You are running the loco from station a) through both contact tracks b) and d) to station c). Then after a delay you have determined the loco starts the travel in the opposite direction, but after passing contact track d) it reverses again and go back to station c) and so on.

On the very first travel from a) does the brake cycle initiate at point d) as it should?

What exactly happens when the loc hits point d) the second time – ie. coming from c)?

Does the loco immediately reverse and go opposite back to c) or does it stop and wait as if it was back at point a)?

Can you see a change of state on port 1 on the config. screen? You probably do with this behaviour, but nothing should happen here when the contact is moved towards point a) only.
You could try and move the contact at d) by hand just after the loc has left point c). If the loco reverses, something seems to be shorting inside the contact track. Have you tried to swap the two contact tracks? If yes and you have the same behaviour at the same place the contact tracks should be OK.

An idea comes to mind. Would it be possible to put the loco upside down next to the track and connect the two track power wires. Then when starting from a) the wheels should run until you move the switch by hand at point d) (observe to move the switch in the travel direction only) - then slow down and stop - wait and run in the reverse. They should then again run until you move the switch at point b). If the wheels do that, your setup is OK. IF, however, the wheels do change direction for no reason maybe a bad timer in the CS is sending rubbish down the line, but it seems unlikely. I think the error lies in the contact track at d).

A bit long winded, but I hope it helps a little.

Edited: just a random thought. You do realize that the two circuits of the contact track are dependent of the travel direction. Only one circuit is to be used on each of the two contact tracks i the shuttle set-up. You havn't by any chance shorted the two tabs together?

Very good Charles I'm happy for you...