From the manual: PLL ERROR. If the radio circuit is unable to tune the AR8200 to the programmed frequency a PLL ERROR (Phase Lock Loop) may result. Check that the problem is not caused by corrupt data stored erroneously in a memory channel, memory bank or search bank. Ensure that sufficient voltage is being provided by the power supply. Failing this, contact your supplier for assistance.
From Strong Signals: # One nasty problem I had on my original 8200 was that the battery saver feature was able to unlock the PLL (a piece of radio circuitry which assures that the radio remains tuned to the requested frequency) which effectively negates the radio's ability to receive a signal
# On my 8200 all I had to do was turn on the power saver, wait for it to go into power saver mode, then turn the squelch fully open or hold down the Monitor key. Instead of opening the squelch and getting a rush of static like you'd expect, the radio would, instead, respond by display "PLL Error". To remove this error, I had to tune to another frequency