True Fitness Z5.4 Owner's Manual page 52

The following service messages will be displayed as they occur,
as well as for the subsequent six safety key insertions. These
messages will be displayed until a key is pressed. Every time these
messages are displayed, a tone will sound twice.
S1:LUBE
This message is displayed when lubrication of the
deck is recommended.
S2:CLEAN
This message is displayed every 500 miles. Prompt
to clean treadmill.
S3:MOTOR This message is displayed every 2500 hours.
Prompt to check motor brushes.
Service Messages
Chapter Seven: Care and Maintenance
Z5.4 & Z5 Treadmill Owner's Guide
Diagnostics
Service
Messages
52