Ford Focus NA C170 Facelift airbag control unit repair

What is a Ford Focus NA C170 Facelift airbag control unit?

The airbag control unit is the central control unit of the restraint system (SRS) in the Ford Focus NA C170 Facelift. It evaluates the signals from the crash sensors, decides within milliseconds in an accident whether to deploy airbags and seatbelt pretensioners, and reports faults via the airbag warning light.

In everyday use the control unit hardly stands out, because it works in the background: at start-up it runs a self-test and then continuously monitors the whole system. If the airbag warning light stays on after start-up, it has detected a fault. The control unit is fitted in the Ford Focus NA C170 Facelift (2008 to 2011). It comes from Bosch.

In an emergency it decides within milliseconds which airbags and seatbelt pretensioners deploy. After an accident it stores crash data and locks itself.

Why is the Ford Focus NA C170 Facelift airbag control unit defective?

The most common cause is crash data stored after an accident, even if no airbag deployed. Ageing electronic components, cold solder joints, moisture and corrosion on connectors, and voltage spikes are other possible causes.

Stored crash data cannot be cleared with an ordinary diagnostic tool, even if the vehicle looks undamaged on the outside. In this case the control unit keeps reporting a fault, although the airbag itself did not deploy.

Voltage spikes occur, for example, through a weak battery or jump-starting. Electronic components age, solder joints can develop cracks over time, and corrosion can form on the connectors in damp conditions. Typical signs are a permanently lit airbag warning light, a fault memory that cannot be cleared, or a diagnostic tool that cannot connect to the control unit.

Common error codes for Ford Focus NA C170 Facelift airbag control unit repair

The error codes of the Ford Focus NA C170 Facelift airbag control unit point to different kinds of faults: internal control unit faults, disrupted communication, interrupted firing circuits of the front airbags and stored crash data. Which code applies in your case can only be determined with a diagnostic tool.

The following list shows error codes that can occur on this vehicle, together with their usual meaning.

• B1342 → Internal fault in the airbag control unit
• U2017 → Memory fault in the restraint system control unit
• B1231 → Crash data stored, event memory locked
• U0151 → Communication with the restraint system control unit interrupted
• B0001 → Driver front airbag, first stage, firing circuit interrupted
• B0002 → Driver front airbag, second stage, firing circuit interrupted
• B0010 → Passenger front airbag, first stage, firing circuit interrupted
• B0011 → Passenger front airbag, second stage, firing circuit interrupted

Error codes are read out with a diagnostic tool. A code alone does not reliably show that the control unit is defective, because connectors, wiring or an airbag module can also be the cause. Only testing the control unit clarifies where the fault lies.

What part numbers are available for the Ford Focus NA C170 Facelift airbag control unit repair?

The part number is printed on the label of the control unit and determines the exact version. Within a model series there are different numbers depending on equipment and year of manufacture.

The following list contains known part numbers for this vehicle. It makes no claim to completeness.

• 8S43-14B321-CA
• 8S43-14B321-BE (Bosch)
• 9S43-14B321-CA (Bosch)
• 9S43-14B321-CC
• AS4Z-14B321-C

Compare the number on the label of your unit with this list. This only ensures that it is the right unit. Whether it is defective is shown only by reading out the fault memory or by testing.

First have the fault memory read out and disconnect the battery. Then remove the control unit, create a repair order online and send the unit in. Testing, repairing and checking at Airbag24 usually take 3–4 working days. 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.