Airbag control unit with part number 4112PC

What is the function of the Airbag Control Unit 4112PC?

The airbag control unit with part number 4112PC is the central control module for the occupant protection system. It continuously processes data from acceleration and seatbelt sensors, deciding within milliseconds whether and which restraint systems—such as airbags or seatbelt pretensioners—need to be deployed in the event of a crash.

As the “brain” of the safety system, this control unit is responsible for processing signals from various crash sensors in the vehicle. These sensors detect sudden decelerations or deformations that indicate a collision.

Based on this information, the unit precisely controls the activation of front, side, or head airbags, as well as pyrotechnic seatbelt pretensioners. The goal is to provide occupants with the best possible protection against injury.

Why does the Airbag Control Unit 4112PC fail?

The most common causes of failure for control unit 4112PC are internal hardware defects, often resulting from overvoltage or moisture damage. Additionally, storing crash data after an accident can lock the unit, making repair unavoidable.

Following a collision—even a minor one—the control unit stores so‑called crash data. This data permanently locks the module to prevent reuse without professional diagnostics, causing the airbag warning light to remain illuminated.

Beyond accidents, internal components on the circuit board may also fail. Overvoltage in the vehicle’s electrical system, aging of electronic parts, or moisture ingress are typical causes of total failure or communication errors.

How do you recognize a defect in the 4112PC control unit?

A defect in the Airbag Control Unit 4112PC almost always manifests as the airbag warning light remaining constantly illuminated in the instrument cluster. Often, the control unit can no longer be read by a diagnostic tool because communication with the vehicle’s CAN bus is disrupted.

The primary and unmistakable symptom is the persistently lit airbag warning light. It does not turn off after starting the engine, indicating a serious system fault and leading to a significant deficiency during the next mandatory technical inspection.

In the workshop, the issue often becomes apparent when no connection can be established with the control unit. The diagnostic tool displays messages such as “Control unit unreachable” or “No communication possible,” strongly suggesting an internal malfunction of the module.

In which vehicles is the 4112PC control unit installed?

The airbag control unit with part number 4112PC is used in vehicles manufactured by Citroën. Specifically, it is found in the first-generation Citroën C4 Grand Picasso models, both in the original version and in the facelifted model.

At Airbag24, we repair the 4112PC control unit for the following specific models:

Citroën C4 Grand Picasso I (model years 2006–2010)

Citroën C4 Grand Picasso I Facelift (model years 2010–2013)

How does the repair of the 4112PC proceed at Airbag24?

At Airbag24, repairing the 4112PC control unit follows a professional process. After careful removal and shipment, the unit undergoes analysis, crash data is erased, and defective components are replaced. Final tests confirm full functionality, backed by 2 years' statutory liability for defects.

Before removing the control unit, the vehicle battery must be disconnected, starting with the negative terminal. A waiting period of at least 10 minutes should be observed to ensure all internal capacitors have fully discharged, guaranteeing safe disassembly.

Upon receipt at Airbag24, the control unit undergoes a thorough incoming inspection. Technicians erase stored crash data and restore the module to its factory settings. If hardware defects are detected, affected electronic components are professionally replaced.

After repair, the unit undergoes comprehensive final testing on specialized test benches to verify proper operation of all system components. We provide 2 years' statutory liability for defects on every repaired unit.