Ford Explorer 4 U251 airbag control unit repair

What is a Ford Explorer 4 U251 airbag control unit?

In the Ford Explorer 4 U251, the airbag control unit is the centre of the restraint system (SRS). It reads the crash sensors, determines within milliseconds of an impact which airbags and seatbelt pretensioners fire, and constantly monitors the condition of the system. Faults are indicated by the airbag warning light.

The unit is fitted in the Ford Explorer 4 U251 (2006 to 2010). The sensors supply it with measurements of the vehicle's deceleration; it compares them continuously and, in an emergency, triggers exactly the restraint devices that suit the situation.

Even in everyday driving the SRS control unit works in the background: it constantly tests itself and the connected components and switches on the warning light if it detects anything unusual. After an accident it stores crash data and locks itself.

Why is the Ford Explorer 4 U251 airbag control unit defective?

Most often the cause is crash data that an accident has left in the unit, even if no airbag was deployed. Ageing electronic components, cold solder joints, moisture and corrosion at the connectors, and voltage spikes in the vehicle electrical system are also possible causes.

It starts with the accident: once crash data has been stored, an ordinary diagnostic tool cannot remove it, and the control unit keeps reporting a fault. Then there is ageing. Over the years electronic components become less reliable, and solder joints turn cold, so that contacts drop out.

Another factor is moisture, which causes corrosion at the connectors and distorts signals. Finally, voltage spikes in the vehicle electrical system put a strain on the electronics, for example from a weak battery or a jump start.

A defect is indicated by an airbag warning light that stays on continuously, a fault memory that cannot be reset, or a diagnostic tool that cannot connect to the control unit. In that case you should have the fault memory read out.

Common error codes for Ford Explorer 4 U251 airbag control unit repair

In the Ford Explorer 4 U251, the codes point to faults inside the control unit, memory problems, disrupted communication, interrupted squib circuits and stored crash data. Which of them occurs in your vehicle becomes clear when the fault memory is read out.

These codes occur in connection with the unit:

• 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 control unit lost
• B0001 → Driver front airbag, squib circuit interrupted
• B0002 → Driver front airbag, second stage, squib circuit interrupted
• B0010 → Passenger front airbag, squib circuit interrupted
• B0011 → Passenger front airbag, second stage, squib circuit interrupted

Error codes are read out with a diagnostic tool. A single code does not necessarily mean that the control unit itself is defective, because connectors, wiring or an airbag module can equally be to blame. Only the inspection shows where the fault lies.

What part numbers are available for the Ford Explorer 4 U251 airbag control unit repair?

You will find the part number on the label on the unit; it determines its exact version. Within one model series there are different numbers depending on equipment and year of manufacture.

Known part numbers for this vehicle are listed here, although the list need not be complete:

• 6L24-14B321-AF
• 6L24-14B321-CB
• 6L24-14B321-GA
• 7L24-14B321-AD
• 7L24-14B321-CA
• 7L24-14B321-DA
• 9L24-14B321-DB
• 9L2Z-14B321-A

Compare the number on your unit with the list. This only tells you whether it is the right unit. Whether there is a defect is clarified only by reading out the fault memory or by the inspection.

The route to repair: first read out the fault memory, then disconnect the battery and remove the control unit. After that, create a repair order online and send in the unit. At Airbag24, testing, repairing and checking 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.