49 CFR § 229.101
Engines
November 18, 2020
(a) The temperature and pressure alarms, controls and related switches of internal combustion engines shall function properly.
(b) Whenever an engine has been shut down due to mechanical or other problems, a distinctive warning notice giving reason for the shut-down shall be conspicuously attached near the engine starting control until repairs have been made.
(c) Wheel slip/slide protection shall be provided on a locomotive with an engine displaying a warning notice whenever required by §229.115(b).