What Is Crash Sensor? – Crash Sensor Explained

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What Is Crash Sensor? – Crash Sensor Explained

Crash Sensor is a safety component in the Supplemental Restraint System (SRS) that detects sudden changes in vehicle acceleration caused by a collision. The sensor sends crash information to the Airbag Control Module (ACM), which decides whether airbags and seat belt pretensioners should be activated.

Crash sensors are also commonly called Impact Sensors. The exact name depends on the vehicle manufacturer.

How Does a Crash Sensor Work?

A crash sensor contains internal electronic components that measure rapid changes in acceleration and deceleration. During a collision, the sensor detects abnormal movement and sends a signal to the SRS control module.

  • Normal driving → stable acceleration signal.
  • Collision detected → sudden acceleration change.
  • ACM analyzes crash data.
  • Airbags and pretensioners may be activated.

Crash Sensor Location

The location depends on vehicle design. Common locations include:

  • Front bumper area.
  • Radiator support area.
  • Front frame rails.
  • Door pillars for side impact sensors.
  • Vehicle center area near the SRS module.

Types of Crash Sensors

  • Front Crash Sensor (FIS): Detects front collision forces.
  • Side Impact Sensor (SIS): Detects side collision forces.
  • Rear Impact Sensor: Detects rear collision forces.
  • Satellite Sensor: Additional sensors used by some manufacturers.

Crash Sensor Signal Flow Diagram

🔴 Battery Power | | ┌────────────────┐ │ SRS / ACM ECU │ └───────┬────────┘ | 🟡 Crash Signal | ┌────────────────┐ │ Crash Sensor │ └───────┬────────┘ | ⚫ Ground

Crash Sensor Diagnostic Procedure

  1. Connect an SRS-compatible diagnostic scanner.
  2. Read stored airbag fault codes.
  3. Check crash sensor communication status.
  4. Inspect sensor connector and wiring.
  5. Check for previous accident damage.
  6. Verify sensor operation using live data.
  7. Clear codes after repair and perform system check.

Live Data Diagnosis (Advanced Scan Tool)

Professional scan tools can display crash sensor information and help determine whether the problem is related to the sensor, wiring, or SRS module.

How To Access Live Data

  1. Connect the scanner to the DLC port.
  2. Select vehicle information.
  3. Open:

    4. System → SRS Airbag → Data Stream / Live Data

Recommended Parameters

  • Crash Sensor Status: Sensor recognition and condition.
  • Communication Status: Connection between sensor and ACM.
  • Sensor Voltage: Supply and signal monitoring.
  • Crash Event Data: Stored collision information.
  • Battery Voltage: Verify stable power supply.

Live Data Interpretation

  • No communication → Check wiring and connector.
  • Incorrect voltage → Check power or signal circuit.
  • Normal data but code returns → Suspect sensor or module.
  • Intermittent data → Inspect wiring movement and corrosion.

Common Crash Sensor Faults

  • Internal sensor failure.
  • Open circuit.
  • Short circuit.
  • Connector corrosion.
  • Water damage.
  • Incorrect installation after repair.

Important Note

Crash sensor wiring, pin numbers, communication type, and sensor values vary between vehicle manufacturers. Always use factory service information before testing SRS circuits.

Related SRS Terms

  • SRS – Supplemental Restraint System
  • ACM – Airbag Control Module
  • Impact Sensor
  • FIS – Front Impact Sensor
  • SIS – Side Impact Sensor

Related DTCs

SRS crash sensor fault codes depend on vehicle manufacturer. See available Airbag DTC articles in the OBDSpark SRS section.

OBDSpark Technician Tip: A crash sensor should not be replaced only because of a code. Always verify wiring, communication, and live data before replacement.

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