P121B Possible Causes
- Faulty fuel injector
- Fuel injector harness is open or shorted
- Poor electrical connection in fuel injector circuit
How to Fix Code P121B?
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
- Engine light on (or service engine soon warning light)
P121B Meaning
The Powertrain Control Module (PCM) monitors the fuel injector. The PCM sets the OBDII code when the fuel injector does not meet factory specifications.