Yes, many things were harder to get a handle on back then. Now we have tools that get us some suggestions, about how to tackle things. Of course, it's up to the viewer to filter out the fluff That's why I personally lean to what the manufacturer might publish, if available. Time is money and trouble shooting will eat you up.
But you can see trailer ABS light on for few seconds when you turn key on, right? If not, trailer ABS light inoperative. Many drivers think it's best repair is to disconnect or mask with tape trailer ABS light.
Check the trailer wheel bearings. If they are worn, the tire will wobble and the ABS sensors will go wonky.
I have a bad sensor on one of my trailer brakes. When I haul through Oregon and go down this one steep grade, I can make it go on every time if I brake too much. It will stay on until the next morning. If I slow down and don't brake as hard I can keep it from coming on.
https://www.thetruckersreport.com/t...stem-abs-light-on.1346490/page-3#post-8220076 Post number 26. Mine acted up when wet. Had corrosion between the wheel sensor and the ABS extension cable to the module. Another time the abs sensor cable had worn against the brake dust cover. I have a ScanGauge D, it was able to capture the abs codes while I was going down the highway so I knew what wheel position to look at for problems.
You can also check the bearings by jacking up the trailer and trying to wobble the rims by hand while they are still bolted onto the axles. They should not wobble at all due to any person's arm strength. If you feel even the slightest movement, the bearing is compromised. This becomes FAR more likely to be the problem if you have noticed uneven wear, with more/irregular wear on the inner edges of the trailer tire tread.