Yaris Diesel fuel consumption issue

Greetings! The symptoms you describe, particularly the higher fuel consumption, reduced power, and check engine light, point towards a potential cylinder pressure fluctuation. It's difficult to say definitively without a diagnostic scan, but I would consider the fuel injectors. Are you experiencing any rough idling or misfires? The problem could also be related to worn piston rings, which would cause a loss of compression. Less likely, but still worth considering, is the camshaft and timing belt. Has the timing belt been changed according to schedule?

Thanks for the quick response! I haven't noticed any rough idling or misfires, so fuel injectors might be less likely. The timing belt hasn't been changed yet, as it's not due for another year based on the manufacturer's recommendations. But what does a timing belt have to do with cylinder pressure? And how would I check the piston rings?

You are correct in noting the absence of misfires, making the injectors less suspect at this stage. Regarding the timing belt, if it's worn or has slipped a tooth, it can affect the valve timing, which directly impacts cylinder pressure. As for checking the piston rings, that requires a compression test. Given the complexity and potential for further damage, especially with a diesel engine, I would strongly recommend taking it to a trusted mechanic for a proper diagnosis. It sounds like a consequential error.

Okay, thanks for the advice. I appreciate the detailed explanation. I took it to a workshop and it turned out to be a faulty sensor causing a cascade of error messages and throwing off the fuel mixture. They replaced the sensor, cleared the codes, and everything's back to normal. No cost!