B12AD Code: Meaning, Causes, and Symptoms | OBD2 Codes

B12AD – Passenger Heated Seat Relay Drive Circuit Shorted To Battery Voltage

 

B12AD Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

B12AD Possible Causes

 

Faulty Heater Seat Relay,Faulty Heater Mat,Heater Mat harness is open or shorted,Heater Mat circuit poor electrical connection,Faulty Heating, Ventilation, and Air-Conditioning (HVAC) Module

 

B12AD Description

 

The Heating, Ventilation, and Air-Conditioning (HVAC) Module contains the passenger heated seat control button and indicator. The heated seat system functions independently from the climate control system. A heated seat relay is located underneath the passenger seat cushion frame. There are 2 voltage supplies to the heated seat relay. Voltage is supplied from the Smart Junction Box (SJB) heated seat relay enable circuit to the passenger heated seat relay coil when the engine is running. The ground is supplied to the opposite side of the passenger relay coil by the HVAC module from the passenger heated seat relay drive circuit when the passenger heated seat switch button is pressed to energize the relay. This closes the relay contacts to supply battery voltage from the SJB circuit to the passenger heater mat circuit. The passenger heater mats are directly connected to ground circuit completing the electrical circuit to heat the seat.