Lewis Hamilton's normally reliable Mercedes suffered a rare failure to hamper the six-time champion's build-up to the new Formula One season.
Taking over from team-mate Valtteri Bottas for the afternoon session on the second day of the second pre-season test at Barcelona's Circuit de Catalunya, Hamilton managed just 14 laps in his W11 before grinding to a halt on track.
The team said in a statement: "We've experienced an oil pressure anomaly which made the engine shut down as a precautionary measure. We're further investigating the issue."
It brought a premature end to Hamilton's running, a day after he and Bottas had completed 189 reliable laps between them on Wednesday, and after Mercedes and Hamilton topped the lap chart from the first test last week with 494 and 273 respectively.
The bulletproof reliability of Hamilton's Mercedes over the last three years has also resulted in him winning successive titles to take his tally to six, with his car suffering just one issue in 62 grands prix.
The latest setback left Hamilton propping up the timesheet of the 13 drivers that took to the track on the penultimate testing day ahead of the season-opening Australian Grand Prix on March 15.
Hamilton said: "Testing didn't quite go to plan today but we will come back better and stronger tomorrow."
The Briton's irrelevant time of one minute 22.425secs was over five and a half seconds adrift of the leading lap set by Sebastian Vettel in his Ferrari.
The four-time champion posted a time of 1:16.841s, using the softest and fastest of the five compounds of tyre Pirelli make available for all the teams during testing, albeit still 1.1s down on the quickest lap of last week set by Bottas.
As on Wednesday, though, Vettel again brought out a red flag for a spin in his SF1000 that sprayed gravel across the circuit, which was one of four stoppages overall during the day, including Hamilton's on-track breakdown.
Max Verstappen beached his Red Bull in the gravel, bringing an end to his morning session after 31 laps before team-mate Alex Albon took over in the afternoon, while Antonio Giovinazzi spun in his Alfa Romeo, hitting a barrier and severely damaging the rear of his car.
Rookie Nicholas Latifi, who had suffered engine issues with his Williams on his previous two outings, enjoyed a trouble-free day, clocking up the most laps with 160.
The 24-year-old Canadian's time on the super-soft tyre of 1:17.313s was good enough for fifth quickest, finishing half-a-second behind Vettel, who managed 145 laps.
