Diagnostic message
Possible cause of error
Remedy
Reference channel error
The reference junction connected at chan‐
nel 0 is faulty due to a wire break, for exam‐
ple.
Check the connections
The reference temperature value transfer‐
red is not within the value range.
Reassign the parameters for the reference tem‐
perature
Underflow
Input value below undershoot range; possi‐
ble cause of error: wrong measuring range
selected
Set another measuring range
With the measuring ranges 4 to 20 mA and
1 to 5 V, if necessary by polarity reversal of
sensor connection
Check the connections
Overflow
Input value exceeds overshoot range
Set another measuring range
Run time calibration error
A wiring fault has occurred on a channel
during the calibration cycle
Eliminate the wiring fault (fault remains until the
next calibration; in other words, a maximum 6 mi‐
nutes or until there is a STOP-RUN transition of
the CPU).
Analog modules
5.17 Diagnostics functions of analog modules
S7-400 Automation System Module Data
226
Reference Manual, Ausgabe 11/2016, A5E00850736-08