Chapter 5: Troubleshooting
Servo Controlled Oxygen
5-18 Service Manual
Oxygen Probe 
Failure
One of the 
sensors is 
reading out of 
range (23-280 
millivolts or the 
difference 
between the two 
O2 sensors is 
above 3%.
Defective Sensor(s) In service mode sensor0 and 
sensor1 should be 23-280. If 
outside this range replace the 
sensors. If in range ensure oxygen0 
and oxygen1 read within 3% of 
each other or replace the sensors.
Leak or occlusion in 
sensor housing area
Be sure sensor housing is seated 
properly and the retaining screws 
are tight. Be sure sensor gaskets 
are in place and the tubing is 
seated correctly in the connectors. 
Check to be sure that the two vents 
in the patient compartment under 
the bed are not occluded. 
Defective cable or 
connection
Measure the voltage at J85.8-
J85.7(sensor0) and J85.6-
J85.7(sensor1) and compare them 
to displayed sensor0 and sensor1. 
If the measurement is the same as 
the displayed, check the cable and 
sensor contacts. 
Defective Servo O2 
board
If the measurement is not the 
same as the displayed, replace the 
Servo O2 board.
O2 Cal Lost-No 
O2
Servo oxygen has 
never been 
calibrated. Servo 
oxygen will not 
operate until 
initial calibration 
is performed.
Perform oxygen 
calibration.
Run calibration.
Alarm Message Meaning Cause Action