Lotus Elise Series 3 airbag control unit repair

What is an Lotus Elise Series 3 airbag control unit?

The airbag control unit in the Lotus Elise Series 3 continuously monitors the entire restraint system (SRS) in everyday driving and, in an accident, triggers the appropriate airbags and seatbelt pretensioners. It runs a self-check when the ignition is switched on and reports faults via the airbag warning light. After an accident it stores crash data and locks itself.

When the ignition is switched on, a self-test runs in which the unit checks its electronics and the connected squib circuits. If the warning light goes out after a short time, the system has passed the test. If it stays on or flashes, a fault has been detected and stored in the fault memory.

In the Lotus Elise Series 3 (2011 to 2021), the control unit also works together with the crash sensors and evaluates their signals. In an accident it decides which restraint systems are deployed.

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

Most often the cause is crash data stored after an accident, even if no airbag was deployed; an ordinary diagnostic tool cannot delete it. Other causes are aged components, cold solder joints, moisture and corrosion on connectors, and voltage spikes.

A weak battery or jump-starting can expose the electronics to voltage spikes. Moisture and corrosion attack above all the contacts of the connectors. With aged components and cold solder joints, the function often fails only gradually.

You can usually tell by the airbag warning light that stays on permanently, by a fault memory that cannot be cleared, or by the diagnostic tool failing to connect. Some lightweight and motorsport versions were delivered without airbags and therefore have no airbag control unit.

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

The codes for the Lotus Elise Series 3 point to two kinds of faults: lost communication with the control unit and faults in the squib circuits of the front airbags. The diagnostic tool reads them from the fault memory.

The following codes are reported frequently. They show which area of the system is affected, but not yet what exactly is failing there.

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

Read out the codes with a diagnostic tool and note down the log. The appearance of a code does not prove that the control unit is defective, because connectors, wiring or an airbag module can also be the cause. The inspection clarifies it.

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

You will find the part number on the label of the control unit. It determines which version is fitted, because depending on equipment and year of manufacture the numbers differ within a model series.

For this model we know the following numbers; the list is not complete.

• A121B0060F
• A138M0195F

Compare the number of your unit with the list. This only ensures that it is the right unit; whether it has a defect only becomes clear from reading out the fault memory or from the inspection.

The process is simple: have the fault memory read out, disconnect the battery, remove the control unit, create a repair order online and send the unit in. As a rule, inspecting, repairing and testing at Airbag24 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.