Renault is unsure of the cause of the engine problem that led to Sunday's Formula Renault 3.5 running to be reduced as a precaution.
Second qualifying and race two were reduced in length at Aragon last weekend as a reaction to several cars suffering high oil consumption in race one, causing reliability issues.
Renault and its FR3.5 engine partner Zytek have started an investigation into the problem, the cause of which was not immediately clear in Spain.
When asked if any changes had been made to the engines over the winter or since the first round of the series at Monza three weeks earlier, Renault Sport Technologies motorsport technical manager Francois Champod said: "No, absolutely not. That's why it's a little bit difficult to understand, because we didn't change anything.
"We will do our best to identify this problem and understand it 100 percent to have all these things solved before the next race in Monaco [on May 26]."
Champod added that while the problem did not affect the whole grid last weekend, there was the potential for that to happen if qualifying and the race had not been shortened on Sunday.
"The engine problem affected not everyone but quite a lot, with the potential for all the field," he said. "[High oil consumption] was the consequence, and this we asked the teams to monitor very closely. It's not a problem of performance, just a problem of potential breakage. [Shortening the race] was not an easy decision to make."