P123D Possible Causes
- Faulty nitrogen oxide (NOx) sensor signal – Linear oxygen sensor
- Nitrogen oxide (NOx) sensor signal – Linear oxygen sensor harness open or short circuit
- Nitrogen oxide (NOx) sensor signal – Poor electrical connection in linear oxygen sensor circuit
How is P123D Code Repair Performed?
Start by checking the “Possible Causes” listed above. Visually inspect the wiring harness and associated connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
- Check Engine Light on (or Service Engine Soon warning light)
P123D Meaning
The Engine Control Module (ECM) monitors the nitrogen oxide sensor. The ECM sets the OBDII code when the nitrogen oxide sensor does not meet factory specifications.