B129B Code: Meaning, Causes, and Symptoms | OBD2 Codes

B129B – Driver Blend Door Actuator Drive Circuit Shorted To Battery Voltage

 

B129B Possible Symptoms

 

Engine Light ON (or Service Engine Soon Warning Light)

 

B129B Possible Causes

 

Stuck or damaged linkage or door,Faulty Blend Door Actuator,Blend Door Actuator harness is open or shorted,Blend Door Actuator circuit poor electrical connection,Electronic Manual Temperature Control (EMTC) Module,Electronic Automatic Temperature Control (EATC) Module

 

B129B Description

 

Under normal operation, to rotate the blend door actuator clockwise, the Electronic Manual Temperature Control (EMTC) Module or Electronic Automatic Temperature Control (EATC) Module supplies voltage to the blend door actuator motors through the door actuator feed A circuits and supplies ground through the door actuator feed B circuits. To rotate the blend door actuator counterclockwise, the EMTC module or EATC module reverses the voltage and ground circuits. The blend door actuator feedback resistors are supplied a ground from the EMTC module or EATC module by the blend door actuator return circuits and a 5-volt reference voltage on the blend door actuator reference circuits. The EMTC module or EATC module reads the voltage on the blend door actuator feedback circuits to determine the blend door actuator position by the position of the actuator feedback resistor wiper arm.