Fuga Hybrid Runs Lean

Running lean on a hybrid Fuga with those symptoms screams fuel delivery issue. First thought: have you checked the usual suspects? I'm talking EGR valve gunked up, old spark plugs, maybe even a clogged catalytic converter restricting exhaust flow. Don't rule out a faulty oxygen sensor either – that can definitely throw off the fuel mixture. Any codes being thrown by the check engine light? That could give you a massive clue. What have you tried already?

Okay, thanks for the tips. I haven't checked the EGR valve yet, but the spark plugs are relatively new. The catalytic converter seems fine, no rattling or anything. Where exactly is the oxygen sensor located, and is it easy to test? Is there anything else to look at regarding fuel delivery?

Okay, so newish plugs and seemingly okay cat. The oxygen sensor is usually located before and after the catalytic converter, screwed into the exhaust pipe. Testing it requires a multimeter and knowing the proper voltage readings for your Fuga – a workshop manual is your friend here. Regarding fuel delivery, since it's running lean, I’m leaning hard towards a defective injection valve/injector not spraying enough fuel. Honestly, with those kms and the lean running code, you're probably best off getting it diagnosed properly at a workshop. They can do a proper fuel pressure test and check each injector. Saves you chasing ghosts.

You were spot on! Took it to the shop, and it was indeed a defective fuel injector. Cost me 515€ to replace, but she's running like new again. Thanks for the help!