Kovalainen raced in the sport for six seasons, winning the 2008 Hungarian Grand Prix for McLaren.
The Finn moved to Caterham but his contract was not renewed at the end of 2012.
But on Wednesday it was announced that Kovalainen will return to the team as a reserve driver, competing in FP1 in Bahrain and Spain.
"There's no plans to race at the moment," he said ahead of his practice run on Friday.
"The plan for me at the moment is to drive Fridays and help the team."
Kovalainen says improving the balance of the CT03 is his main priority, but he will not receive the full upgrades until Barcelona.
"We had a quite well-balanced car last year although it was still lacking performance. The comments from the race drivers this year is that it's very difficult to find a balance. That will be the first thing I'm looking for. In Barcelona I will have a full update on the Friday, so I will get a back-to-back with this car and then the full, new package."
The Finn says he initially declined a role, but watching the sport from home restarted his interest and he discussed the role with team owner Tony Fernandes.
"We talked about this for the first time a long time ago. At the very beginning I wasn't interested in this type of role. But when you're sitting at home for a couple of months watching other people drive the car, it makes you think 'I'd actually like to have a go'.
"Just before Malaysia, I had a chat with Tony and I said 'Do you think I could do something for the team still? The idea we had earlier?' And he said 'sure'."
Kovalainen denies that his presence will put pressure on regular drivers Charles Pic and Giedo van der Garde.
"I'm here to help the race drivers right now. It's different to what it was before. I'm working 100 per cent for the team and I'll try to give all I can to help the race drivers and help the team."
But Kovalainen insists that despite having no race plans, he still wants a race seat.
"Of course I want to race. Being here puts me in a better position if a race drive ever becomes available here, or even somewhere else. But right now I have no plans to race."