Hilux high fuel consumption hissing noise

Sounds familiar! I had similar symptoms on my Hilux. Have you checked for air leaks in the intake system? That hissing noise makes me think it's a vacuum leak somewhere. I would check for cracks on the air intake hose first. It's a common issue.

Intake hose, huh? Where exactly is that located? And could that really cause all those problems?

Yep, it's between the air filter box and the intake manifold. The leak messes with the air-fuel mixture, causing the poor fuel economy and the check engine light. The hissing is the air escaping. I'd get it checked out by a mechanic if you're not comfortable doing it yourself, but I bet that's the culprit. I had mine fixed for around 100€.

Thanks for the tip! I got the intake hose checked. It was exactly that. All fixed now!