[Elecraft] K1 error message

[km5ps]

I have a K1 that here the last few days I have been getting the message 
after ATU tuning.  The display shows  PL0.  Tonight I noticed the ATTN 
light barely flickering.  I have it connected to a 12 volt battery in my 
truck threw the cigarette lighter.  I have been running the K1 mobile 
some.  I was just getting this on 20 meters some but now on 40 also.  I 
have not been able to get it to do it at home hooking it to a 12 v 
battery with same size cable.  I have looked through the manual and can 
not find this error code.  I thought it might mean low power output or 
low battery power since the ATTN light started to flicker but truck was 
running so should be plenty of power.  I am going through the manual 
again tonight to see if I can find anymore information about it.  Any 
suggestions would be great.

Thanks
John