B1209 - Frontal Collision Detection

Repair Importance Level: 3/3

Repair Difficulty Level: 3/3

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Possible causes

Faulty Air Bag Diagnosis Sensor Unit (ACU)

Air Bag Diagnosis Sensor Unit (ACU) harness is open or shorted

Air Bag Diagnosis Sensor Unit (ACU) circuit poor electrical connection

What does this mean?

Tech notes

After a front collision, all the deployed components and the Air Bag Diagnosis Sensor Unit (ACU) must need to be replaced. If there is no collision, then the problem is with the Air Bag Diagnosis Sensor Unit (ACU)

What does this mean?

Possible symptoms

Air Bag Warning Light ON

B1209 Description

Detects component damage resulting from a front collision, blinks or illuminates the air bag warning lamp to

inform the driver. The air bag and seat belt pre-tensioners for driver and front seat passenger are operated by the decision of the Air Bag Diagnosis Sensor Unit (ACU) out signal transmitted because of the frontal collision.

The Frontal Collision Detection consists of crash zone sensor, Air Bag Diagnosis Sensor Unit (ACU), air bags and seat belt pre-tensioners for driver and front passenger.

OBDII Code B1209 - Frontal Collision Detection - AutoCodes.com

B1209 Information for specific makes

B1209 INFINITI Frontal Collision Detection

B1209 NISSAN Frontal Collision Detection

Precautions for SRS “AIR BAG” and “SEAT BELT PRE-TENSIONER” Service

Never probe the electrical connectors on air bag, side air curtain modules or seat belts.
Never disassemble or tamper with safety belt buckle/retractor pretensioners, adaptive load limiting retractors, safety belt inflators, or probe the electrical connectors.
Do not use electrical test equipment to check SRS circuits unless instructed to in this Service Manual.
Before servicing the SRS, turn ignition switch OFF, disconnect both battery cables and wait at least 3 minutes. For approximately 3 minutes after the cables are removed, it is still possible for the air bag and seat belt pre-tensioner to deploy. Therefore, do not work on any SRS connectors or wires until at least 3 minutes have passed.

Failure to follow this instruction may result in the accidental deployment of these modules, which increases the risk of serious personal injury or death.

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