C70 rough running drift compensation error

Rough running and a check engine light after only 66072 km on a diesel C70 points to a few possibilities. The drift compensation error suggests issues with your fuel injectors. The ECU uses drift compensation to adjust for slight variations in injector performance over time. It attempts to compensate, but if an injector is failing, it can't adjust enough, hence the error. Have you noticed any changes in fuel consumption or any unusual exhaust smoke?

Fuel consumption seems normal, no weird smoke. Is this drift compensation thing something I can fix myself, maybe with a scan tool?

While a scan tool can read and clear the error code, 'resetting' the drift compensation isn't a fix. It's a symptom. The ECU will just relearn the drift again, and the problem will return if an injector is faulty. Given the symptoms and the error code, a defective injector is the likely cause. Unfortunately, diagnosing a specific injector often requires specialized equipment and knowledge. I'd recommend taking it to a workshop for proper diagnosis and repair.

Thanks for the advice. Took it to a shop, and you were right – faulty injector. Cost me 515€ to replace. Runs fine now.