Corolla diesel engine issues

Hey there, I drive a Corolla as well, though I don't know if this helps because it's a different year. Your symptoms sound pretty close to what I went through a while back. Rough idle and sluggishness, like the engine was struggling. Have you tried replacing the filter itself, just to rule that out? It's like checking if your pipes are clogged before calling a plumber for the whole house.

Thanks for the input! No, I haven't replaced the filter yet, only checked the connections. Was it definitely the filter in your case, or something else causing those symptoms?

Well, in my case, the filter replacement didn't fully fix it, but it helped a bit. The issue was indeed the heater element. The connections looked fine but the mechanic suggested that the heater can be faulty internally. I'd suggest you get it checked in a workshop, especially if you suspect the heater is the problem and the error is stored in the system. Don't want to fry anything.

Thanks! So, I took it to a mechanic. Turns out it was indeed a defective connection and they did have to replace the fuel filter. The whole thing cost about 95€. Now it runs like new!