Airbag control unit with part number A4518200185

What does the airbag control unit A4518200185 do?

The airbag control unit A4518200185 is the control unit of the restraint system (SRS) in Smart. It evaluates the crash sensors and determines in the event of an accident which airbags and seatbelt pretensioners are triggered.

The decision takes only milliseconds. In the background, the unit monitors the entire system continuously.

If the system detects a fault, the airbag warning light in the instrument cluster comes on. The entry remains in the fault memory until it is read out or rectified.

After an accident, the control unit stores crash data and locks itself.

Why does the control unit A4518200185 fail?

The most common cause is crash data stored after an accident, even if no airbag has deployed. A normal diagnostic tool does not erase it.

Storing crash data does not mean that the electronics are defective. It does, however, block regular access, so only a repair removes the data.

Aged electronic components can also fail. Cold solder joints, moisture and corrosion on plug connectors lead to contact faults.

Voltage spikes are a further factor, for example with a weak battery or a jump start.

How can you tell that the A4518200185 is defective?

A defect shows up as the airbag warning light, which stays on permanently or intermittently, as error messages in the instrument cluster and as a diagnostic tool without connection to the control unit. A fault memory that cannot be cleared is also an indicator.

These signs can occur together:

• airbag warning light that stays on permanently or intermittently
• error message in the instrument cluster
• no connection between diagnostic tool and control unit
• fault memory cannot be cleared

With a defective control unit, airbags and seatbelt pretensioners may possibly not trigger in an emergency. This fact alone justifies a prompt check.

Which vehicles is the A4518200185 fitted in?

The airbag control unit A4518200185 is fitted in these vehicles: Smart Fortwo C451 (2007-2015).

The following vehicles are on record for this part number:

• Smart Fortwo C451 (2007-2015)

Have the fault memory read out before removing the unit. This shows reliably whether the control unit is really defective or a plug or a cable is at fault. Then compare the part number on the label of the removed unit with A4518200185.

For the same vehicles, we also repair control units with the part numbers A451 820 24 85, A4518201585/001, A4518202285, A4518202485/002, A4519011300Q02.

How does the repair of the A4518200185 work?

Before removal, you read out the fault memory and attach the log. Then you disconnect the battery, remove the control unit, create the repair order online and send the unit in well packed. Airbag24 checks and repairs the unit and returns your own control unit to you.

Work carefully when removing the unit so that the plugs and housing are not damaged.

At Airbag24, the unit is examined on the test bench. Defective components are replaced, the crash data is deleted and a function test is carried out. Processing usually takes 3–4 working days, and this time applies only to checking, repairing and testing.

Our repairs come with 2 years' statutory liability for defects. 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.

How does the control unit A4518200185 get to Airbag24?

You send the unit as a parcel, or book a UPS collection for an extra charge. After the repair, Airbag24 returns it by UPS.

Enclose the printed repair order in the parcel and pack the unit shock-proof.