Toyota iQ Camshaft Sensor Failure

Sounds like a plausible cause given the symptoms! A faulty camshaft sensor can definitely mess with engine control. When the engine control unit (ECU) doesn't get the right signal from the sensor, it can't properly time the fuel injection and ignition, leading to poor starting and stalling. Have you tried checking the wiring to the sensor? A loose connection or damaged wire could also be the culprit. Also, any idea what the error code is?

Thanks for the quick reply! I did a quick visual check of the wiring, but didn't see anything obvious. I don't have a proper diagnostic tool to read the error code myself. Where exactly should I be probing with a multimeter to properly test the sensor?

Without the code, it’s guesswork. Testing the sensor can be tricky without knowing the expected values, plus you don't want to damage anything. Given the symptoms and your suspicion about the encoder wheel, it might be beyond DIY territory. If the wheel itself is damaged, that's not a simple sensor replacement. At this point, it might be best to have a workshop take a look. They'll be able to properly diagnose the issue and confirm if it's the sensor, the wheel, or something else entirely.

Thanks, that's what I was afraid of. I dropped it off at the shop today; they confirmed the camshaft sensor was indeed faulty and that the encoder wheel was defective. Repair cost is estimated at 695€. Ouch, but at least it'll be fixed properly!