Diagnostics and Troubleshooting -
Revision 19 HC900 Process Controller Installation and User Guide 177
06/14
Bad I/O Channel Diagnostics
Individual channels on I/O modules indicate their diagnostics by 6 flashes on the Scanner and CPU; the
channel’s LED does not indicate a diagnostic. Table 32 is a list of conditions that can cause a bad channel
diagnostic.
Table 32 – Bad I/O Channel Diagnostics
Module
Type
Failure message
indicated on
Honeywell OI or
Honeywell
HCDesigner/Utilities
function block monitor
Description User Action
AI Burnout Failure The sensor – T/C, RTD, or mV source --
is failing burnout checks.
Check terminal block
connections
Replace source element
Replace module.
Under range The signal at the terminals is less than
10% below the range of the sensor.
Check the signal level being
applied to the terminals.
Replace module.
Over range The signal at the terminals is more than
10% over the range of the sensor.
Check the signal level being
applied to the terminals.
Replace module.
Failing to convert When attempting to take a reading, the
ADC fails. This could result if the incoming
signal is either too large or small. It also
could result if the ADC circuit is failing. If
the problem is the ADC circuit, most likely
other channels will have the same failure.
Check the signal level being
applied to the terminals.
Replace module.
AO Bad Channel The board indicates that the channel is
failing to output the correct value.
Check terminal connections.
Replace module.
DO Bad Channel The number of configured channels in the
DO function block exceeds the number of
hardware channels on the DO card.
Reconfigure the DO function
block.
Replace DO card with correct
number of channels.
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