P121B Code: Meaning, Causes, and Symptoms | OBD2 Codes

P121B – Cylinder Balance Test Injector Blocked

 

P121B Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

P121B Possible Causes

 

Faulty Fuel Injector,Fuel Injector harness is open or shorted,Fuel Injector circuit poor electrical connection

 

P121B Description

 

The Powertrain Control Module (PCM) monitors the Fuel Injector. The PCM sets the OBDII code when the Fuel Injector is not to factory specifications.