FIS (Front Impact Sensor) – Function, Symptoms, Location, and Diagnosis

The FIS (Front Impact Sensor) is a key component of the Supplemental Restraint System (SRS). It detects frontal collision forces and sends crash information to the Airbag Control Module (ACM). The ACM uses this data, together with inputs from other sensors, to determine whether the airbags and seat belt pretensioners should deploy.

What Does FIS Stand For?

FIS = Front Impact Sensor

Main Functions

• Detects frontal vehicle impacts.
• Sends impact data to the Airbag Control Module.
• Works with left and right front impact sensors.
• Helps determine airbag deployment timing.

Common Symptoms of a Faulty FIS

• Airbag warning light remains ON.
• SRS fault codes stored in the ACM.
• Airbag system may be disabled.
• Communication or impact sensor circuit faults.

Typical Location

The FIS is typically mounted at the front of the vehicle behind the bumper or on the radiator support. Depending on the vehicle, one or more front impact sensors may be installed.

Simple Signal Diagram

 Front Collision
       │
       ▼
+------------------+
|       FIS        |
+------------------+
       │ Signal
       ▼
+------------------+
| Airbag Control   |
| Module (ACM)     |
+------------------+
       │
       ▼
 Airbags / Pretensioners

Diagnosis Tips

• Read SRS fault codes with a compatible scan tool.
• Inspect the sensor connector and wiring.
• Check for collision damage near the sensor.
• Replace the sensor if it fails manufacturer tests.

Important Note

Front impact sensor location, wiring, connector pinout, and operating values vary by vehicle manufacturer and model. Always refer to the factory service manual before diagnosis or replacement.

Related SRS Components

• LFIS – Left Front Impact Sensor
• RFIS – Right Front Impact Sensor
• ACM – Airbag Control Module
• Seat Belt Pretensioner
• Clock Spring

Frequently Asked Questions

What is the purpose of the FIS?

It detects frontal impacts and sends crash information to the Airbag Control Module.

Can a bad FIS cause the airbag light to turn on?

Yes. A faulty FIS can trigger the SRS warning light and store diagnostic trouble codes.

Is the FIS the same on every vehicle?

No. The number, location, and wiring of front impact sensors vary between vehicle manufacturers and models.