KAB (Knee Air Bag): Operation, Location, and Diagnostic Guide

KAB, which stands for Knee Air Bag, is a safety component in modern Supplemental Restraint Systems (SRS). It is designed to protect the driver's or passenger's knees and lower legs during a severe frontal collision by reducing impact forces.

What Is a Knee Air Bag (KAB)?

A Knee Air Bag is a small airbag installed in the lower dashboard area. During a crash, the SRS control module activates the knee airbag along with other restraint systems to help maintain a safer occupant position and reduce injuries.

Where Is the Knee Air Bag Located?

The KAB is usually installed:

• Below the steering column on the driver side
• Inside the lower dashboard panel
• In some vehicles, on the passenger side lower dashboard

The exact location and design can vary depending on the vehicle manufacturer and model.

How Does the Knee Air Bag System Work?

The knee airbag system depends on signals from crash sensors and the SRS control module.

Knee Air Bag Signal Flow:

Impact Sensors
↓
SRS Airbag Control Module
↓
KAB Deployment Circuit
↓
Knee Air Bag Inflator
↓
Occupant Protection

Main Components of KAB System

• Knee Air Bag Module
• SRS Control Module
• Crash Sensors
• Wiring Harness and Connectors
• Airbag Deployment Circuit

Common Knee Air Bag Problems

• Knee airbag circuit open or short
• Damaged wiring connector
• High resistance in the deployment circuit
• SRS module communication faults
• Previous airbag deployment

How to Diagnose KAB Faults

1. Use an SRS-compatible diagnostic scanner.
2. Read stored airbag trouble codes.
3. Check wiring and connectors according to manufacturer procedures.
4. Test the SRS system after repairs.

Important Safety Warning

The Knee Air Bag is an explosive safety device. Never test an airbag inflator directly with a multimeter or apply external power to the circuit. Always follow manufacturer repair procedures.

Related SRS Components

• Driver Air Bag (DAB)
• Passenger Air Bag (PAB)
• Side Air Bag (SAB)
• Seat Belt Pretensioner
• Crash Sensor

FAQ

Is KAB the same as a normal airbag?

No. KAB is a specialized airbag designed mainly to protect the knees and lower legs.

Does every vehicle have a Knee Air Bag?

No. Availability depends on vehicle design, safety standards, and manufacturer specifications.

Can a KAB fault turn on the SRS warning light?

Yes. Any fault in the knee airbag circuit can cause the SRS warning light to stay illuminated.