SEPANG, Malaysia (REUTERS) - Lewis Hamilton recovered from a frustrating morning session to lay down a marker to his Formula One rivals with the fastest time of the day in second free practice for the Malaysian Grand Prix on Friday.
Mercedes team-mate Nico Rosberg had dominated the first session, in which Hamilton was unable to set a timed lap after suffering a major engine problem and stopping on the track.
After mechanics worked to fix what his team deemed a "hardware issue", Hamilton slipped on the quicker medium tyres and clocked an impressive 1min 39.790sec with 20 minutes remaining to top the time sheets.
Ferrari will have been buoyed by their day's work with a resurgent Kimi Raikkonen finishing second in each session, lapping 0.373sec behind Rosberg in the morning and by the same margin adrift of Hamilton in the afternoon.
Sebastian Vettel also looked quick in the other Ferrari, backing up his impressive debut at the season-opening Australian Grand Prix with the third-fastest time of the morning.
The German also spun off while on target for a very quick time later in the day.
Rosberg followed his earlier impressive run with a third-fastest time but a mistake on his flying lap on the medium tyres prevented him from challenging Hamilton's best work around the sweeping 5.543 km Sepang International Circuit.
Fernando Alonso enjoyed a smooth return to action after missing the season-opener due to concussion caused by a crash in winter testing, the Spaniard racking up the laps in his McLaren to finish 14th in the morning session.
Alonso did have a minor scare when he locked up and skidded into the pit lane entrance late in the second session but he and team-mate Jenson Button remained firmly among the back markers with their Honda-powered cars showing just a slight overall improvement since Melbourne.
It was also a notable day for Manor Marussia, who despite setting the slowest times of both practice sessions, were able to get their modified 2014 cars out on the track after failing to even manage that in Australia.
Despite leading the way, Hamilton complained of "downgraded shifts everywhere" over the team radio on his return to the pits and will have lingering fears of the reliability issues that cropped up in a disappointing first practice.
The Briton ground to a halt at the Turn Nine hairpin after starting the session without telemetry and complained of an issue at the rear of the car.
The stricken Mercedes was returned to the garage on a flat-bed truck and quickly stripped down by mechanics, who set about repairing Hamilton's engine ahead of the second session.
Of the other teams, Williams showed improvement as the day progressed as Valterri Bottas, also returning from injury, was fifth fastest with team-mate Felipe Massa just behind.
Red Bull also looked a little more competitive than they had in Melbourne with Daniel Ricciardo overcoming "weak traction" to finish sixth in first free practice and his Russian team mate Daniil Kvyat managing fourth in the later session.