Travellers into work suffered widespread disruption after yesterday's 7.42am from East Kilbride to Central station was at the centre of the fire scare near the city's Crossmyloof station.
ScotRail said a false alarm in the fire detection system led to water being sprayed on to the engine, causing steam to be emitted from under the carriage.
More than 20 firefighters were called to Crossmyloof after the alarm was raised.
All services on the line, including trains from Giffnock, Thornliebank, and Pollokshaws West were stopped following the incident.
The train driver raised the alarm at around 8.15am yesterday.
Incident commander, Station Manager Stephen Carson, said: "We received a call from Network Rail reporting a fire in the engine compartment of a train.
"The train's firefighting system had alerted the driver and activated its automated foam extinguishing equipment.
"Firefighters ensured the affected engine was isolated and that passengers were safely evacuated from the train to the nearby station.
"First Scotrail engineers checked the train.
"Specialist engineers were able to strip down the affected part of the train to establish the cause of the incident.
"We understand their investigation found a faulty sensor had activated the fire suppression system and raised the alarm."