While test driving the vehicle I was unable to get the crawl control to engage. I would place the vehicle in 4L and then in Drive before hitting the crawl control button. The display kept saying the vehicle had to be in "D" or "R" to engage even though I was already in drive. Also, the vehicle is beeping non stop while in 4L. I've been trying research what might be causing this (operator error vs. issue with the vehicle itself) but I'm not having much luck.
First thing Is to ensure that you are in neutral when you switch to 4lo. If, while in neutral, you push the button down and move the switch into 4lo position, it may take a few seconds, but you should here the actuator and then you should see the dash lights indicating that you are in 4lo. Only then should you switch to Drive or Reverse.
If you were in neutral and moved the switch to 4lo and then engaged Drive and it was still beeping, then it sounds like it might be the actuator. It’s possible that 4lo has never been engaged before. There are a few threads on here about this issue. A couple of things you can try:
- ensure that the truck has been running and is warmed up before engaging 4lo
- try to engage 4lo and have somebody outside the truck listen for the actuator
- try to drive around with 4lo engaged
- engage 4lo and the turn the truck off for a minute and then back on again
I wouldn’t fool around with CC until you are certain that 4lo is actually engaging. My money is on a stuck actuator due to lack of use. Once the actuator is working, everything else will be fine, although you are likely to have a similar issue with the center diff. For sure, if 4lo hasn’t been used much, then the center diff lock has not been used and the actuator is probably going to be stuck as well.
I experienced both of these issues when I bought my truck but once the actuators started working, I never had issues again. While I don’t use the center diff lock very much in practice, I still engage it every now and then when I am on dirt or gravel just to prevent it from sticking again.
edit - Sorry, forgot that you said you had a 100 before so you probably know to put it in neutral first.