Renault is making good progress on the engine faults that plagued the four-day Formula One test in Spain a fortnight ago but is still behind schedule, according to media reports.

The problems affected all three Renault-powered teams in Jerez, with champions Red Bull forced to end the first pre-season test of the season early having barely completed any laps.

Mercedes-powered cars accounted for 875 laps in Spain while the Renault equivalent only managed 151.

Renault supplies Red Bull, Toro Rosso, Caterham and Lotus although the latter did not take part in the tests.

The French supplier has been working hard on a fix and is confident its teams will spend more time on the track in testing in Bahrain this week.

“Mainly we were facing hardware issues and consequently also software issues,” head of track operations Remi Taffin was quoted as saying.

“The first one was the energy store problem. We have had good upgrades that we could test... and everything worked as expected.

“We are now confident the problems we had in the first test are solved when we look into the hardware and especially the energy store.

“The next chapter was obviously software. In the first test we had some poor driveability that was mainly traced to either boost control and calibration issues which we have taken on for the last two weeks and we have improved.”

Formula One has a new ‘power unit’ – a 1.6 litre V6 turbo with complex energy recovery systems – this season to replace the tried-and-tested 2.4-litre V8 engines.

Since the problems in Jerez, Renault has run promotional days with Lotus and Toro Rosso with mixed success and, while Taffin said they were still behind schedule, it was not as bad as first thought.

“We are still behind schedule but it’s not a question of months,” he explained.

“Maybe we are now three weeks behind and we are on a plan to recover.

“We are now going to go into Bahrain with what we would like to have finished the first test with.”