"I think they have tried to improve the reliability on that part.
"So for that part - the MGUH - we are allowed three in the season so we have used one of those and that means that later in the year there could be a penalty."
Hartley finished a disappointing 15th in Melbourne but a first-lap pit stop due to a flat-spotted tyre and a puncture later in the race took him out of the fight for the minor placings.
The 28-year-old feels he would have been in the fight for 12th or 13th had he not had those issues.
"I think after Barcelona testing we thought we were definitely in that midfield battle and that was confirmed really in Melbourne," the Le Mans winner said.
"Qualifying 16th was somewhat disappointing because we were so close to getting through to Q2 and having that option to fight from 15th to 10th position but it showed we were in that little battle from 12th to the back of the field, which is extremely tight.
"The brief from Toro Rosso from very early on was that the start of the season was going to be very difficult for us - there had been a lot of changes over the winter break including a new power plant, which is a big task over the winter months to incorporate that new power unit and everything that goes along with it so we knew that the start of the season could be tricky.
"I would still say there are a lot of positives and knowing there are a lot of updates to come I would still like to think that we will be moving up the field as the year goes on."
Although he went to Melbourne with the goal of scoring a maiden championship point he concedes that goal wasn't overly realistic. Despite that, the goal for Bahrain this weekend is to score a point again as he feels their car might be more suited to the Middle Eastern track.
"I think Bahrain might suit us a bit better. I like to think tyre management is one of my stronger suits - there are a lot of low speed corners in Bahrain, which has been one of the stronger points of the Toro Rosso Honda. "The goal this weekend will be the same as it was in Melbourne - trying to score points."