B1278 Code: Meaning, Causes, and Symptoms | OBD2 Codes

B1278 – Headlight Switch ON Position Circuit Malfunction

 

B1278 Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

B1278 Possible Causes

 

Faulty Combination Headlight Switch,Combination Headlight Switch harness is open or shorted,Combination Headlight Switch circuit poor electrical connection,Faulty Multiplex Integrated Control Unit (MICU)

 

B1278 Description

 

The Multiplex Integrated Control Unit (MICU) monitors the Headlight Switch Position. The MICU sets the OBDII code when the Headlight Switch Position is not to factory specifications.