I would check to make sure as the program runs it’s not miss interpreting bits. If you use the Stream OP Code (148) it produces a check sum. I would Change to stream and verify that you still get >20,000 with a correctly computed check sum. If you are getting correct check sums and high values post your code it could be something on how it’s being ...
Found the answer to my own question.
The iRobot needs to be in Safe or Full mode in order to control the LEDs.
So, I was entering the numbers correctly (139 4 0 254), but needed to send the command for Safe (131) or Full (132) first.