Lotus Exige Series 3 airbag control unit repair

What is an Lotus Exige Series 3 airbag control unit?

In the Lotus Exige Series 3, the airbag control unit handles the central control of the restraint system (SRS). It evaluates the signals from the crash sensors, decides within milliseconds in an accident which airbags and seatbelt pretensioners deploy, and shows faults via the airbag warning light.

How can you tell that this unit suddenly matters? Usually the airbag warning light in the instrument cluster stays on permanently, or the fault memory contains an entry that can no longer be cleared. The control unit is fitted in the Lotus Exige Series 3 (2012 to 2021) and continuously monitors the entire restraint system, that is, sensors, squib circuits and the associated connections.

After an accident, the unit stores the crash data and locks itself. That is exactly when the warning light shows that the system is no longer ready for use and that you should put the vehicle right before the next journey.

Why is the Lotus Exige Series 3 airbag control unit defective?

In most cases the cause is crash data that was stored after an accident, even if no airbag deployed. An ordinary diagnostic tool cannot clear it. Other causes are aged electronic components, cold solder joints, moisture, corrosion on connectors and voltage spikes.

Voltage spikes occur, for example, when the battery delivers little power or the vehicle needs a jump start. Moisture and corrosion mainly attack connectors and then disturb communication within the system. Aged components and cold solder joints cause the unit to fail its self-test.

If the airbag warning light no longer goes out, the fault memory cannot be cleared or the diagnostic tool cannot make contact with the control unit, these are the typical signs. This vehicle has one particularity: some lightweight and motorsport versions were delivered without airbags and therefore have no airbag control unit at all. So first check whether your vehicle is equipped with airbags at all.

Common error codes for Lotus Exige Series 3 airbag control unit repair

The error codes show where the restraint system is faulty. They concern communication with the control unit and the squib circuits of the front airbags. You can read out which code is stored from the fault memory with a diagnostic tool.

For this vehicle series, the following codes occur most often:

• U0151 → Communication with the airbag control unit lost
• B0001 → Driver front airbag, first stage, firing circuit faulty
• B0010 → Passenger front airbag, first stage, firing circuit faulty

A code alone does not prove that the control unit is defective. A fault at a connector, a wire or an airbag module can trigger the same message. Only testing the unit clarifies where the fault actually arises.

What part numbers are available for the Lotus Exige Series 3 airbag control unit repair?

The label on the control unit bears the part number. It determines which version of the unit it is, and depending on equipment and year of manufacture there are different numbers within the model series.

We know the following part numbers for this vehicle; the list makes no claim to completeness:

• A121B0060F
• A138M0195F

Check whether the number on your label appears in the list. That tells you nothing more than which unit it is. A defect can only be established after reading out the fault memory or when testing in our workshop.

Please keep to this order: first have the fault memory read out, then disconnect the battery, and then remove the control unit. After that you create the repair order online and send the unit to us. As a rule, processing at Airbag24 takes 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.