A week or two ago the truck started in limp mode (M and S and D and red indicator lights on shifter all flashing) - I restarted and it went away

It was good until yesterday, now all starts are now in limp mode - the truck acts normally (aside from all the flashing lights and being sluggish in first gear)

Several years ago when this happened I had to have my alternator rebuilt, years later I had to have new ends on my battery cables

I checked the battery cables - they look fine - I checked the charge on the battery (Optima Yellow Top from several years ago) and it was 11.8 V which seemed low so I put my intellegent charger on it

When checking these I noticed that the ABS pump motor relay is making a faint, rapid beeping sound at around 170 beats per minute - if I pull it the sound stops, if I swap another relay in it starts ago - I now realize this is a sound I've heard for years and always thought it was just a quiet dripping sound - any thoughts? is this normal?

After being on charge for a little bit, my suspension compressor (I don't have an air suspension) motor relay started making making a clunking sound when the charge cycle was ending so I stopped the charge and the clunking ended - any thoughts? is this normal?

I also noticed that coming off my engine compartment fuse box battery connector there is a small red wire with badly damaged (very bent, but possibly still functioning) 10 A fuse running to small box beside the battery with a number of coloured wires coming off it - what is this?

Anyway, not sure I got any closer to my limp mode issue - anything I should try before taking it into the shop?

Thanks again!

TDC