Husqvarna FE 450 EU Owner's Manual page 103

22 BLINK CODE
Blink code FI warning
lamp (MIL)
Error level condition
45 FI warning lamp (MIL) flashes 4x long, 5x short
FE EU, FE 501 AUS
Lambda sensor heater cylinder 1, sensor 1 - short circuit to ground or open circuit
FE EU, FE 501 AUS
Lambda sensor heater cylinder 1, sensor 1 - input signal too high
101