Fault code U1218 – a step-by-step guide to diagnosing and fixing it

Error code U1218 is displayed and the check engine light is on - what does this mean?

DTC U1218 is recognized by the OBD/EOBD system when a communication error occurs in the vehicle's CAN bus network. This error code relates to data transmission between different control units and may have slightly different meanings for different manufacturers, but generally refers to network communication problems.

What causes can this error code have?

• Defective CAN bus cabling
• Damaged plug connections in the network
• Faulty control units
• Corroded contacts in the connections
• Interrupted or short-circuited cables
• Defective CAN bus terminating resistor
• Voltage problems in the vehicle electrical system
• Malfunctions due to electromagnetic interference

What symptoms occur in parallel with error code U1218?

• Communication problems: Various vehicle systems do not function properly or fail completely
• Warning lights: Multiple indicator lights illuminate simultaneously on the dashboard
• Functional failures: ABS, ESP, air conditioning or other electronic systems operate unreliably
• Starting problems: The vehicle may not start or may run rough
• Missing displays: Certain information is not shown on the display

How can I fix the problem with error code U1218?

• Repairing trouble code U1218 requires a systematic diagnosis of the CAN bus network.
• Carry out a complete CAN bus diagnosis: Check all control units for communication errors using a professional OBD scanner and identify defective modules, then replace faulty control units
• Check wiring and plug connections: Visually inspect all CAN bus cables for damage, corrosion or loose connections, repair or replace damaged cables and clean and firmly connect all plug connections
• Measure terminating resistors: Check CAN bus terminating resistors with a multimeter for correct resistance value (typically 120 ohms) and replace defective resistors
• Check the vehicle electrical system voltage: Test battery and alternator to ensure that all control units are supplied with stable voltage, replace corresponding components if problems occur
• Test individual control units in isolation: temporarily disconnect suspicious modules from the network and check whether the error code disappears, program or replace defective control units