Fault code U1205 – a step-by-step guide to diagnosing and fixing it

Error code U1205 is displayed and the check engine light is on - what does this mean?

The DTC U1205 is a network-related fault code that is recognized by the OBD and EOBD systems when a communication problem occurs in the vehicle's CAN bus network. This trouble code indicates a faulty data transmission between different control units, which can affect the vehicle functions.

What can cause this error code?

• Defective CAN bus cable or cable break
• Corroded or loose plug connections in the network
• Faulty CAN bus resistor (termination resistor)
• Defective control unit in the communication network
• Damaged CAN bus wiring due to mechanical impact
• Short circuit in the network cabling
• Defective gateway or communication node
• Malfunctions due to electromagnetic interference

Which symptoms occur in parallel with error code U1205?

• Communication faults: Various vehicle systems do not function properly or respond with a delay
• Warning lights: Multiple indicator lights may illuminate simultaneously
• Starting problems: The vehicle may not start or may start erratically
• Instrument panel failures: Gauges in the instrument panel do not function properly or display incorrect values
• System failures: ABS, ESP, air conditioning or other electronic systems operate incorrectly

How to fix the problem of fault code U1205?

• Repairing fault code U1205 requires a systematic diagnosis of the CAN bus network.
• Perform a complete CAN bus diagnosis: Use a professional OBD scanner to check all control units for communication errors and identify defective modules
• Check and repair cable connections: Check all CAN bus plug connections for corrosion, looseness or damage and clean or replace if necessary
• Replace CAN bus cabling: Locate damaged or severed CAN bus cables and replace with new, specification-compliant cables
• Measure and replace termination resistors: Check the 120 ohm termination resistors on the CAN bus and replace defective resistors
• Replace defective control unit: After identifying the faulty module, replace the corresponding control unit and have it reprogrammed
• Eliminate sources of electromagnetic interference: Identify and remove retrofitted electronic devices or defective components that cause interference