It was the second interruption is as many days for new recruit Jolyon Palmer, who racked up 42 laps - less than one third of Nico Rosberg’s tally for Mercedes - as a result.
Palmer had suffered software issues on day one, which he later described as "painful", admitting: “It was a disappointing first day - such a messy day.
"I'd hoped to have done more than 37 laps. We'd definitely have liked to have got more under our belt."
With Palmer due to hand over to Kevin Magnussen for the third and fourth days of the first test, he will therefore have just two further days of testing before the season opener in Australia on 18-20 March.
Palmer’s red flag - brought out when he coasted to a smoky halt between Turns 2 and 3 - was not the only one on day two in Barcelona: Max Verstappen also caused a stoppage when his Toro Rosso hit trouble early in the morning, but he was able to quickly get back underway, breaking into triple figures in the lap count in the afternoon.