Frijns, the 2012 Formula Renault 3.5 champion, contested a partial GP2 season with Hilmer last year.
He was a Sauber F1 reserve in 2013, but his only running came in the Silverstone young driver test, whereas his Caterham programme will include some Friday practice outings.
Caterham considered Frijns for F1 race seat
Asked if he would race anywhere else this year, Frijns replied: "I'm concentrating fully on my test role for Caterham.
"So I will do a few FP1s and try to help the team as much as I can."
Caterham has signed Alexander Rossi, who will share F1 test/reserve duties with Frijns, and Rio Haryanto for its GP2 arm this year.
Frijns made his Caterham F1 debut in testing at Jerez on Thursday, but did not manage a flying lap due to the electronics problems the team and engine supplier Renault struggled with all week.
"You're not enjoying a day when you're driving 60km, but I enjoyed my day with the team," he said.
"I had some fun even though there wasn't a lot of running. They worked hard."
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