Lionel polar express o gauge locomotive

The PCB/I.R. trigger detects movement inside loco to send a chuff signal.  If you were only missing chuff sound this might be where to look.  I suspect you have no sound but believe your speaker in the tender is operational.  I would look into your drawbar.  There are reports of failures in this area.  Here is a link to one:

https://ogrforum.ogaugerr.com/...9#168670231919030239

Thank you Steims. So, I puy an ohm's meter from the plug to the draw bar and get a reading on one side of the drawbar and then switch the wire in the plug and get a reading on the other side. Do you think that the new board could be bad? Thank's again, John.

I certainly hope the new board isn’t bad and maybe the old board is still good.  Maybe it’s just a connection issue between board and drawbar or drawbar to sound card.    I have no steamers that have a IR drawbar so I don’t have any advice on how to troubleshoot that.  Others hopefully will chime in.

Check the sound switch in the back of the cab. Check continuity where the wires are soldered on the switch. move the switch make sure continuity goes away. I think if you pull the switch harness plug out of the PCB. The default will be sound. If you remove the plug, hook the tender up and pull the speaker plug and check continuity through the plug. Should be 8 ohms, same as your speaker. The “IR” is the chuff switch located up by the smoke unit. It is operated by a cam on the axle of the front wheel that operates a lever.

Thank you both for your help. I'll let you know what I find.