GMI V!SA Manual De Instrucciones página 53

Note: If a "ZERO FAULT" flag is displayed together with
a flashing spanner symbol on any of the
other sensors, follow instructions detailed in
paragraph 3.4.2.
The faulty CO2 sensor will cause the instrument to display
a flashing 'ZERO FAULT' flag alternating with a gas value
to warn the user that this sensor is not correctly zeroed,
as shown in Fig. 3.7:
Fig. 3.7 CO2 Sensor - Zero Fault
alternating with
ALARMS
3-11