Fault code U0155 – a step-by-step guide to diagnosing and fixing it

Error code U0155 is displayed and the check engine light is on - what does this mean?

The DTC U0155 indicates that there is a communication error between the vehicle's control unit and the instrument cluster. The OBD system recognizes that there is no or faulty data transmission via the CAN bus network. This EOBD fault code can occur with various manufacturers and affects the display functions in the cockpit.

What can cause this fault code?

• Defective instrument cluster control unit
• Damaged CAN bus cables between control units
• Loose or corroded plug connections on the instrument cluster
• Faulty ground connections in the vehicle network
• Faulty fuses for the communication system
• Software errors in the instrument cluster
• Overvoltage damage due to defective alternator
• Water damage to the instrument cluster

What symptoms occur in parallel with fault code U0155?

• Failed displays: Speedometer, rev counter or other instruments do not work
• Lighting problems: Cockpit backlighting fails
• Warning lights: Various indicator lights remain permanently on or off
• Missing information: On-board computer does not display data such as fuel consumption or range
• Starting problems: Vehicle may not start due to lack of communication
• Electronic malfunctions: Other control units also report communication errors

How can the problem with error code U0155 be rectified?

• The repair requires a systematic diagnosis of the communication network in the vehicle.
• Checking and replacing defective fuses for the instrument cluster and CAN bus system
• Cleaning and fixing all plug connections on the instrument cluster and applying contact spray
• Measuring the CAN bus lines with a multimeter and repairing damaged cables between the control units
• Replacement of the complete instrument cluster in the event of irreparable hardware defects
• Software update or reprogramming of the instrument cluster control unit via diagnostic device
• Checking and repairing the vehicle ground connections, especially on the dashboard
• Checking the vehicle electrical system voltage and repairing the alternator in the event of overvoltage or undervoltage