B1340 Code: Meaning, Causes, and Symptoms | OBD2 Codes

B1340 – Left Air Temperature Actuator


B1340 Possible Symptoms


Engine Light ON (or Service Engine Soon Warning Light)


B1340 Possible Causes


Faulty Left Air Temperature Actuator,Left Air Temperature Actuator harness is open or shorted,Left Air Temperature Actuator circuit poor electrical connection,Faulty Instrument Panel Module (IPM)


B1340 Description


The Instrument Panel Module (IPM) controls the HVAC door actuators to regulate the airflow through the Heating, Ventilation, and Air Conditioning (HVAC) system. Each actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference, control, 5-volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5, or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer’s adjustable contact changes the door position signal between 0-5 volts. The IPM converts the voltage values to count values where one volt is approximately equal to 51 counts. The IPM uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.