U0155 airbag control unit fault

What does error code U0155 mean?

Error code U0155 indicates a loss of communication with the instrument cluster control module, technically referred to as “Lost Communication with Instrument Panel Cluster (IPC) Control Module.” The airbag control unit (SRS) can no longer send or receive data via the CAN bus to or from the speedometer, leading to critical malfunctions and classified as safety‑relevant.

Technically speaking, U0155 means there is an interruption on the data line between the SRS module and the IPC. This data exchange is essential because the instrument cluster controls warning lights such as the airbag indicator and forwards information from other systems to the airbag control unit.

Since the airbag system contains pyrotechnic components, any work on these parts must be performed exclusively by trained professionals. Disrupted communication can compromise the proper functioning of the entire restraint system in the event of a crash.

What symptoms appear with U0155?

The main symptom of error U0155 is a sporadically or continuously illuminated airbag warning light. Often, this is accompanied by malfunctions in the instrument cluster during driving, such as a flickering or completely failing speedometer. In some cases, the engine starts only briefly before stalling immediately, or the transmission shifts jerkily.

The most noticeable sign is the activated airbag warning light on the dashboard, indicating that the system has detected a fault and may not be fully operational.

Another typical symptom is the failure of the speedometer or other displays in the instrument cluster. These failures can occur suddenly while driving and are clear evidence of disrupted communication on the CAN bus.

Less obvious but still common accompanying issues include starting problems or erratic shifting behavior in automatic transmissions. These result from other control units also relying on signals from the instrument cluster.

What causes U0155?

The most common cause of error code U0155 is physical damage to wiring or connectors—such as broken cables, loose connections, faulty plugs, or corrosion. Only after that do defects in the instrument cluster itself, blown fuses, or, more rarely, internal faults in the airbag control unit come into consideration.

In most cases, the problem lies in the wiring harness connecting the airbag control unit to the instrument cluster. Damage incurred during previous repairs—for example, on doors—or connectors loosened by vibrations can disrupt signal transmission.

Interference on the CAN bus, affecting communication with other modules like the ABS or engine control unit, can also trigger U0155 as a secondary fault. A comprehensive diagnosis of the entire bus system is therefore often necessary.

A defect in the electronics of the instrument cluster (IPC) itself is another frequent cause. Less commonly, the airbag control unit is the culprit, although in certain models internal electronic faults within the SRS module can directly lead to this error code.

Which models experience U0155?

Error code U0155 occurs across brands but is particularly well documented in specific models from Škoda and Jaguar. Notably affected are the second-generation Škoda Octavia and the luxury Jaguar XJ of the X351 series. At Airbag24, we professionally repair this fault for the aforementioned vehicles.

At Airbag24, we repair error code U0155 for the following specific vehicle models:

Škoda: Octavia Combi Mk2, Octavia RS Mk2

Jaguar: XJ Supersport X351, Daimler XJ X351

How is error U0155 repaired?

A professional repair begins with a systematic diagnosis to pinpoint the exact source of the fault—whether it’s the wiring, the instrument cluster, or the airbag control unit. If the control unit is the root cause, Airbag24 analyzes and repairs it at the component level, including re-soldering or replacing defective parts, followed by a functional test.

The first step in the workshop is reading the fault memory using a suitable diagnostic tool such as VCDS. This is followed by a visual inspection of wiring and connectors, along with testing relevant fuses and relays using a multimeter.

If the diagnosis points to an internal defect in the airbag control unit, repair is the most cost-effective solution. After sending the unit to Airbag24, the control unit is opened, and the circuit board is examined for faulty solder joints, defective chips, or capacitors.

The defective electronic components are professionally replaced or re-soldered. Upon completion of the repair and successful testing, the fault memory is cleared. We provide 2 years' statutory liability for defects on all repairs.