Fault code B1620 – a step-by-step guide to diagnosing and fixing it

Error code B1620 is displayed and the check engine light is on - what does this mean?

The DTC B1620 is a body control module fault code that is recognized by OBD and EOBD systems and indicates a fault in the electrical system of the air conditioning system. This trouble code mainly concerns the communication between the air conditioning control unit and other vehicle systems. This fault code can have slightly different meanings for different manufacturers, but usually refers to air conditioning control problems.

What causes can this fault code have?

• Defective air conditioning control unit
• Damaged cable connections to the body control module
• Loose or corroded plug connections
• Failed air conditioning temperature sensor
• Faulty blower motor control unit
• Faulty evaporator temperature sensors
• Short circuit in the air conditioning wiring
• Defective relay in the air conditioning system
• Problems with CAN bus communication

What symptoms occur in parallel with fault code B1620?

• Air conditioning system failure: The air conditioning system no longer works or works irregularly
• Blower problems: The blower does not start or only works at certain levels
• Temperature control: Uneven or no temperature control in the vehicle interior
• Electronic displays: Missing or faulty displays on the climate control panel
• Noise development: Unusual noises from the air conditioning system

How can the problem of error code B1620 be rectified?

• The repair requires a systematic diagnosis of the electrical components in the air conditioning system.
• Inspection and replacement of the defective air conditioning control unit by a specialist workshop
• Check and repair all cable connections between the air conditioning system and body control module
• Cleaning or replacement of corroded plug connections in the air conditioning system
• Replacement of defective temperature sensors in the air conditioning system according to the manufacturer's specifications
• Repair or replacement of the blower motor control unit
• Checking and calibrating the CAN bus communication between the control units
• Replacing defective relays and fuses in the air conditioning circuit