Polestar 4 1st generation airbag control unit repair

What is a Polestar 4 1st generation airbag control unit?

The Polestar 4 1st generation airbag control unit is the central control unit of the restraint system (SRS). In an accident, it decides within milliseconds, based on the crash sensors, which airbags and seatbelt pretensioners to deploy. It then stores crash data and locks itself.

This emergency is the task the unit was built for. In normal operation, by contrast, it monitors the system continuously, even while driving. If it detects a deviation, it switches on the airbag warning light and logs the fault in the fault memory.

The control unit is installed in the Polestar 4 1st generation (since 2024). Because it controls the entire restraint system, a fault can affect several functions. If the warning light is on, however, the cause does not have to lie in the control unit itself. Sensors, wiring or connectors may also be responsible.

Why is the Polestar 4 1st generation airbag control unit defective?

The most common cause is crash data stored in the Polestar 4 1st generation airbag control unit after an accident, even if no airbag deployed; an ordinary diagnostic tool cannot erase it. Ageing electronic components, cold solder joints, moisture with corrosion at connectors and voltage spikes are also possible causes.

An accident leaves its traces in the unit's memory. Only the repair removes this condition. It is indicated by the airbag warning light.

A weak battery or a jump start, for example, can cause voltage spikes. If moisture gets into connectors and the contacts corrode, signals arrive distorted or not at all. If components age or cold solder joints crack, intermittent faults develop over time that do not go away on their own.

A defect is indicated by a permanently lit airbag warning light, a fault memory that cannot be cleared, or a diagnostic tool that cannot connect to the control unit. If you notice this on your Polestar 4 1st generation, you should have the unit checked.

Common error codes for Polestar 4 1st generation airbag control unit repair

On the Polestar 4 1st generation, the codes point to two types of fault: interrupted communication with the airbag control unit and a faulty firing circuit in the restraint system. The code shows where the system detected the fault.

The codes in the following list are known; the list makes no claim to be complete.

• U0151 → Communication with the airbag control unit lost
• B15381B → Restraint system firing circuit open or resistance too high

Error codes are read out with a diagnostic tool. A single code does not prove that the control unit is defective, because connectors, wiring or an airbag module can also be behind it. Only an inspection brings clarity.

What part numbers are available for the Polestar 4 1st generation airbag control unit repair?

You will find the part number, which defines the exact version, on the label of the control unit. Depending on equipment and year of manufacture, the numbers also differ within one model series. On the Polestar 4 1st generation, you read it from the removed unit and state it in the repair order.

We do not yet have any part numbers on file for this vehicle. Please therefore note the number from the label after removal and enter it in the repair order. This ensures that it is the matching unit. Whether it is actually defective is shown by reading out the fault memory and by the inspection.

The path to the repair looks like this: First, have the fault memory read out. Then disconnect the battery from the vehicle electrical system and remove the control unit. Afterwards, create a repair order online and send the unit to us. Checking, repairing and testing usually take 3–4 working days at Airbag24. Your own control unit is returned, not a different one.

The repaired control unit comes back with all vehicle data and is ready for use as soon as it is refitted — no coding or programming is required.