Alarm Message Meaning Cause Action
Oxygen System
Failure 1
The sensor
plug thermistor
temperature
reading is out
of the range:
15C-55C.
Unit is cold: <15
degrees C.
Allow unit to warm up.
Cooling fan is not
running when the
sensor housing
temperature gets
above 50 degrees.
Test the cooling fan. Refer to the Tips section
4.7.3.3.
Defective sensor plug
thermistor or cable.
Disconnect the cable and measure the
resistance of the thermistor between J85.4
and J85.5. Refer to R/T chart in the Tips
section 4.7.3.4. If sensor is shorted, open, or
values don’t agree with the R/T chart, replace
the sensor plug assembly or the cable.
Defective servo O2
board.
If resistance is in range replace the servo O2
board.
Oxygen System
Failure 2
The RH reading is
out of valid range:
1-99. When out of
range it displays 0
in service mode.
Defective sensor plug.
Measure the humidity sensor voltage
between J85.2 and J85.1. If the voltage is
outside the range of 0.7V- 4.0V, replace the
sensor plug assembly.
Defective servo O2
board.
If it is in the correct range, replace the servo
O2 Board.
Oxygen System
Failure 3
The checksum test
performed during
power up testing
failed.
Defective
Microcontroller.
Replace microcontroller U6 on the Servo O2
board.
Oxygen System
Failure 4
Analog to digital
converter circuit
self test failed. The
reading of Vtest
is out of the valid
range: 1.216V-
1.254V.
Defective Servo O2
board.
Replace servo O2 board.
Check O2
supply
After calibration,
both supply
valves are
opened and after
approximately 20
seconds, sensor1
reading is not
greater than 23%.
O2 supply is not
connected.
Verify O2 supply, minimum 45psi (310kPa) is
connected to the inlet.
© 2001 by Datex-Ohmeda, Inc.. All rights reserved. 6600-0356-000 103 61
Chapter 4: Troubleshooting
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