DIAGNOSIS The battery pack is not communicating with the tool. The red status LED on the pack is flashing a fault code.
FIX Remove the battery. Press and hold the battery fuel gauge button for 5 seconds. This resets the battery management system. Reattach it firmly to the tool until it clicks. Try the tool again.
IF THAT DIDN'T WORK The fault is likely a bad cell group in the lithium-ion pack. You need a new 12V Max Bosch battery. The tool will not work with a permanently faulted pack.
HEADS UP Do not try to disassemble or repair the battery pack. The lithium-ion cells are sealed and pose a serious fire risk if damaged.