The Finn, who has been a leading race driver at the team since its Team Lotus inception in 2010, was dropped for 2013 in favour of pay-drivers Charles Pic and Giedo van der Garde.
31-year-old Kovalainen, however, is now back in a reserve and testing role.
He drove in Friday practice recently in Bahrain, and on Friday in Barcelona he will drive again, at the wheel of Frenchman Pic's car.
He said he hopes an upgrade package for the Spanish grand prix puts Caterham back ahead of usual rival Marussia.
"The car itself is basically the same as last year's," Kovalainen is quoted by Turun Sanomat newspaper.
"The monocoque is the same, only the aerodynamics were modified. So it's no surprise the team has not gone so well, when you're putting an old car against the new ones."
Kovalainen confirmed that Caterham's approach to this year has been deliberate.
"The team is trying to stay - with the least possible effort - in the top ten this year and put more effort into next year," he said.
"The new car is being developed already.
"When the rules change so much, it's important for us to get started with the new car as quickly as possible."