Carrier Weathermatic 8000 error code

Hi, Last night outside temp. dippped near freezing. During the night expected furnace to kick in but it did not. When checked, control board is flashing error code 31. Well, can't find the manual in a hurry as usual, LOL. Can any one give me a pointer on this error code? TIA, Tony
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.