P121E BMW Possible Causes
- Faulty nitrogen oxide (NOx) sensor Linear oxygen sensor
- Nitrogen oxide (NOx) sensor Linear oxygen sensor harness open or short circuit
- Nitrogen oxide (NOx) sensor Linear oxygen sensor circuit poor electrical connection
How to Fix BMW P121E 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)
P121E BMW Meaning
The engine control module (ECM) monitors the nitrogen oxide (NOx) sensor linear oxygen sensor. The ECM sets the OBDII code when the nitrogen oxide sensor linear oxygen sensor does not meet factory specifications.