Ricciardo reported a loss of power before being called in, ending the longest active run of successive race finishes on the grid.
Speaking at the time, team principal Andreas Seidl indicated a problem on the chassis side of the power unit, though further investigations would be carried out.
With those now complete, the German reaffirmed the issue was limited to a cracked pipe.
“After the race we found a cracked pipe on the chassis side of the power unit installation,” he confirmed.
“We didn't find a cracked monocoque, which I read somewhere.”
The problem has been resolved for this weekend's Qatar Grand Prix, and there are no ongoing ill-effects.
That was punctuated by an issue for Norris, when the Brit ran wide at Turn 15 and clattered the underside of the car on the kerbing.
An emergency switch was triggered in the car, along with the moment causing damage to the bodywork, though he was able to roll into the pit lane where the car was repaired.
Title rivals Ferrari meanwhile were sixth and seventh fastest, the better part of 0.5s clear of Norris in the leading McLaren.
Practice continues in Qatar at 01:00 AEDT on Saturday morning.