P121C BMW Possible Causes
- Faulty nitrogen oxide (NOx) sensor
- Nitrogen oxide (NOx) sensor wiring harness is open or short-circuited
- Poor electrical connection in the nitrogen oxide (NOx) sensor circuit
How to Fix BMW P121C Code?
Start by checking the “possible causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
- Check engine light on (or service engine soon warning light)
P121C BMW Meaning
The engine control module (ECM) monitors the nitrogen oxide (NOx) sensor. The ECM sets the OBDII code when the nitrogen oxide sensor does not meet factory specifications.