A new battery usually helps but even a brand new battery can still give poor performance in cold weather.
Err 2 is as stated before the second sensor not seeing the projectile, first check alignment, second clean the lens! I have found lead dust settling makes the sensors rather less sensitive no matter what light or battery condition.
I only ever bother with my Chrony when I need a downrange velocity to assess BC of a pellet, it can be a royal pain to get a reading when shooting from a distance even with a rested gun carefully sighted against a target behind the Chrony.
BSA Super10 addict, other BSA's inc GoldstarSE, Original (Diana) Mod75's, Diana Mod5, HW80's, SAM 11K... All sorted!
Well, I cleaned the sensors, shook it a bit, tried every 9v battery in the house - twice - then once I was totally mixed up over which batteries were old vs new - the bloody thing started working on it's own accord!
[] AL [] - [] AL [] - [] AL [] -
Stupid thing has put me literally hours behind schedule.
Now it's after 8pm and I have gun spread all over the kitchen table, when it should be my dinner... or a hooker.
Get a Combro - cost next to nothing, and mine has never failed under any light or none
Just a thought, Phil.
As yours is a fold up chrony, have you checked for a break in the wires to the rear sensor ?
If it is your actual sensor buggered I have a scrap Prochrono here we can rob next weekend if we need.
To buy a Combro!