Rear Impact Sensor (RIS) – Function, Symptoms, Location, Diagnosis, and Possible DTCs

The Rear Impact Sensor (RIS) is an SRS (Supplemental Restraint System) component used in some vehicles to detect rear-end collisions. It sends impact information to the Airbag Control Module (ACM), which uses the data to manage occupant protection systems such as seat belt pretensioners and, on certain vehicles, additional safety functions.

What Is a Rear Impact Sensor?

RIS = Rear Impact Sensor

Main Functions

• Detects rear-end collision forces.
• Sends impact data to the Airbag Control Module (ACM).
• Supports seat belt pretensioner activation on some vehicles.
• Works together with front and side impact sensors.

Common Symptoms

• Airbag warning light ON.
• SRS diagnostic trouble codes stored.
• Seat belt pretensioner system fault.
• Communication or sensor circuit errors.

Typical Location

The Rear Impact Sensor is typically mounted near the rear body panel, rear luggage compartment, rear frame rails, or inside the trunk area. The exact location varies depending on the vehicle manufacturer and model.

Simple Signal Diagram

 Rear Collision
       │
       ▼
+------------------+
|       RIS        |
+------------------+
       │ Signal
       ▼
+------------------+
| Airbag Control   |
| Module (ACM)     |
+------------------+
       │
       ▼
 Seat Belt Pretensioners
 Other Safety Functions

Possible Diagnostic Trouble Codes (DTCs)

• B1635 – Rear Impact Sensor Circuit (manufacturer-specific)
• B1636 – Rear Impact Sensor Signal Fault
• B1637 – Rear Impact Sensor Internal Fault
• Manufacturer-specific SRS communication codes

Diagnosis Tips

• Scan the SRS system using a compatible diagnostic tool.
• Inspect the rear sensor connector for corrosion or water intrusion.
• Check the wiring harness for damage or open circuits.
• Replace the sensor if internal failure is confirmed.

Important Note

Not all vehicles are equipped with a dedicated Rear Impact Sensor. Many manufacturers rely on the Airbag Control Module's internal accelerometers or use different sensor configurations. Sensor location, wiring, and DTC definitions vary by manufacturer and model.

Related SRS Components

• FIS – Front Impact Sensor
• LFIS – Left Front Impact Sensor
• RFIS – Right Front Impact Sensor
• LSIS – Left Side Impact Sensor
• RSIS – Right Side Impact Sensor
• ACM – Airbag Control Module

Frequently Asked Questions

Does every vehicle have a Rear Impact Sensor?

No. Many vehicles do not use a dedicated rear impact sensor and instead rely on internal crash sensors within the Airbag Control Module.

Can a faulty Rear Impact Sensor turn on the airbag warning light?

Yes. If the vehicle is equipped with one, a malfunction can illuminate the SRS warning light and store diagnostic trouble codes.

Can the Rear Impact Sensor be repaired?

Most manufacturers recommend replacing a faulty sensor rather than attempting repairs.