Lotus Exige Series 2 airbag control unit repair

What is an Lotus Exige Series 2 airbag control unit?

The airbag control unit in the Lotus Exige Series 2 is the central control unit of the restraint system (SRS): it links sensors, squib circuits and airbags into one system. In an accident it deploys the airbags and seatbelt pretensioners; otherwise it monitors everything and reports faults via the airbag warning light. After an accident it stores crash data and locks itself.

The crash sensors continuously send signals to the control unit. It evaluates them within milliseconds and triggers the squib circuits of the airbags and seatbelt pretensioners accordingly. Without this interplay, no restraint system would deploy in an emergency.

The unit is fitted in the Lotus Exige Series 2 (2004 to 2011); it comes from Siemens VDO. Besides deployment, self-monitoring is also one of its tasks, because every detected fault is stored.

Why is the Lotus Exige Series 2 airbag control unit defective?

Most often the cause is stored crash data: it stays in the unit after an accident, even if no airbag deployed, and cannot be erased with an ordinary diagnostic tool. Other causes are ageing of the electronics, cold solder joints, moisture and corrosion at connectors, or voltage spikes.

Voltage spikes can occur, for example, with a weak battery or when jump-starting. Moisture acts over the long term, because contacts oxidise and contact resistance builds up. Older electronics and cracked solder joints lead to dropouts that the unit registers as a fault.

One sign of a defect is the airbag warning light staying on permanently. A fault memory that cannot be cleared, or a diagnostic tool that cannot connect, also points to it. Please note that not every vehicle of this model range has airbags: an airbag control unit is only fitted in vehicles with airbag equipment.

Common error codes for Lotus Exige Series 2 airbag control unit repair

On the Lotus Exige Series 2, the codes concern the squib circuits of the front airbags. They are read out with a diagnostic tool and show in which area the system has detected a fault.

These codes appear in the fault memories of these vehicles.

• B0001 → Driver front airbag, firing circuit faulty
• B0010 → Passenger front airbag, firing circuit faulty

Please note that a single code does not clearly prove the control unit to be the cause. A faulty connector, a damaged wire or an airbag module can produce the same entry. That is why only the inspection of the unit decides.

What part numbers are available for the Lotus Exige Series 2 airbag control unit repair?

Every control unit carries a part number on its label that defines the exact version. Because the numbers within a model range differ by equipment and year of manufacture, read this information off before sending the unit in.

The list below shows known numbers for the Lotus Exige Series 2; it is not exhaustive.

• A121B0060F

Check whether the number on your label appears there. This only confirms the correct unit. Only reading out the fault memory or the inspection shows whether a defect is present.

Until the repair, proceed as follows: read out the fault memory, disconnect the battery, remove the control unit, create a repair order online and send the unit in. Inspecting, repairing and testing usually take 3–4 working days at Airbag24.

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.