The 41-year-old's Ferrari F138 suffered a gearbox failure in the morning, which caused a small fire, and there were initially concerns that the damage might have prevented the car running again today.
But after a gearbox change, de la Rosa took to the track in the afternoon for his first serious laps.
"When I stepped out of the car on the installation lap after the gearbox broke, I was not feeling very happy because you wait for an opportunity like this for all your life, then suddenly after a few corners you have to step out of the car," said de la Rosa.
"I was very, very excited but then I had a low, then the mechanics did a fantastic job to turn the car around and we had a sensible afternoon, which is critical because of how expensive one day of testing is nowadays.
De la Rosa added that he was happy with his own performance despite his programme including data gathering runs and aerodynamic tests that prevented him setting an eye-catching time.
"I was very happy at the end to do quite competitive laps, for the conditions we were running in," he said.
"There is a scientific approach behind the test - it's not just 'throw Pedro in the car'."
F1 editor Edd Straw
It was very strange to see Pedro de la Rosa decked in the red of Ferrari and even the man himself was clearly delighted by the experience of driving one of Maranello's finest.
In a sport that is so often cold, clinical and cynical, to see a 41-year-old who knows in his heart that he has most probably started his final grand prix reveling in getting behind the wheel to do an important job for this great team, was a real feel-good moment.
The ex-Arrows, Jaguar, McLaren, Sauber and HRT racer has a vital role to play and no less a judge than Fernando Alonso recognised that de la Rosa was the perfect man to play the central role in development of Ferrari's simulator.
This was no charitable act from Ferrari, but a smart move that should help to close the gap in factory-based technologies that has played a part in it not winning a championship since the in-season testing ban.
And if it can give an affable, popular and very capable veteran an experience that he has waited for his whole career, and probably never thought was going to happen, then that can only be a good thing.