1. There are, I believe, 3 heaters in the DEF/SCR system

2. Shops make a diagnosis, tell you what they are going to do- YOU approve the repairs. When they have guessed wrong, you still pay. Arguably the thinking is that it is the car's fault that it is hard to repair. they may also claim "oh, there is more than one broken part". Whatever. To answer your question, it is common.

3. So what does 46c4 mean? Is it a bad heater code? Is it an error being detected in how the SCR system detects a blockage and then activates the heater? Dunno.

FYI: https://www.newtis.info/tisv2/a/en/e...system/XOk5tV8