Airbag control unit with part number 391035

What is the function of Airbag Control Unit 391035?

The airbag control unit with part number 391035 is the central control module for the occupant restraint system (SRS) in the Fiat Tempra 159. It processes data from crash sensors and is responsible for precisely and promptly deploying airbags and seatbelt pretensioners in the event of a collision, thereby protecting occupants.

As the brain of the passive safety system, this module continuously monitors all connected components. It performs a self-test each time the vehicle is started. If all systems are functioning correctly, the airbag warning light in the cockpit will extinguish after a few seconds.

If a fault occurs in the system or crash data is stored following an accident, the control unit locks the system for safety reasons and permanently illuminates the warning light.

What defects occur in Control Unit 391035?

Typical defects of Control Unit 391035 include stored crash data after an accident that prevents further operation, communication failures with diagnostic tools (error codes 65535, B1000), and internal electronic malfunctions. The latter can be caused by overvoltage or component aging.

The most common cause of failure is the storage of crash data. After a collision, the unit locks itself permanently to prevent erroneous deployment in the future. This data cannot be cleared by standard diagnostic equipment at workshops.

Another critical issue is complete loss of communication. The control unit no longer responds to requests from diagnostic tools. Often, error code 65535 or B1000 (control unit defective) is then logged in the fault memory of other control units.

Internal electronic faults are also widespread. Causes may include damage from overvoltage, insufficient supply voltage, or age-related wear of hardware components such as capacitors on the circuit board. These problems affect Fiat models like the Tempra and Ducato equally.

How do you recognize a defect in Airbag Control Unit 391035?

The clearest symptom of a defect in Control Unit 391035 is a permanently illuminated airbag warning light in the instrument cluster. Additionally, communication with the control unit often becomes impossible, and errors stored in the fault memory cannot be cleared, effectively disabling the entire airbag system.

The airbag warning light (SRS light) remains on after engine start-up and does not extinguish as expected following the system check. This indicates a serious, safety-critical malfunction.

Another telltale sign is that a specialized workshop’s diagnostic tool can no longer access the airbag control unit. The module is unreachable for diagnostic queries, making detailed fault analysis impossible.

Due to the detected fault, the entire restraint system is proactively deactivated. In this state, airbags and seatbelt pretensioners are no longer functional, posing a significant safety risk.

In which vehicles is Control Unit 391035 installed?

The airbag control unit with part number 391035 was specifically developed for the Fiat Tempra. It is used in both sedan and station wagon (SW) variants of the 159 series produced between 1990 and 1996. Matching the part number is crucial for compatibility.

At Airbag24, Control Unit 391035 is repaired for the following Fiat Tempra model series:

Fiat Tempra 159 (model years 1990–1993)

Fiat Tempra 159 Facelift (model years 1993–1996)

How is Control Unit 391035 professionally repaired?

Professional repair includes diagnosis on specialized test benches, clearing crash data, and resetting the unit to factory settings. For hardware defects, affected electronic components are replaced. This process is significantly more cost-effective than replacing the entire unit while preserving the original vehicle coding.

After submission to Airbag24, the control unit undergoes a standardized repair procedure. First, an initial inspection verifies the reported fault. It is recommended to attach a workshop fault report to expedite diagnosis.

The core of the restoration involves expertly erasing stored crash data and resetting the internal memory. If diagnostics reveal a hardware defect—such as faulty capacitors or other circuit board components—technicians replace these parts.

A major advantage of this approach is that the vehicle’s original programming and coding remain intact. As a result, the repaired control unit can be reinstalled without requiring extensive reprogramming. Each repair comes with 2 years' statutory liability for defects.