Honda HR-V: SRS System Description - SRS Unit (KA/KC)

System Diagram

• Power supply circuit: Provided to maintain power when battery voltage is low or in case of power supply damage due to a collision.
• Front impact G sensor and side impact G sensor: Detects impact to the SRS unit as acceleration, and converts it to electrical signal.
• Microprocessor: An impact decision algorithm decides whether or not the collision signal warrants deployment of the airbags or the tensioners.
• Diagnostic circuit: Performs self-diagnosis to determine whether system abnormalities are present. If an abnormality is detected, the SRS indicator in the gauge control module turns on.
• Non-volatile memory: Records fault conditions. The SRS memories are not erased even if the 12 volt battery terminal is disconnected.
• Communication circuit: Circuit for outputting or deleting memory contents.

Fig. 1: SRS System Diagram

When airbags or tensioners are about to be deployed, a large amount of current passes through the SRS unit. After the airbags and tensioners are deployed, the interior of the SRS unit is damaged, and must be replaced.

Automatic Short-Circuit Mechanism of SRS Unit Connectors

When the SRS unit connectors are disconnected from the SRS unit, the automatic short-circuit mechanism in the connectors creates short-circuits to prevent accidental deployment of an airbags or tensioners.

This automatic short-circuit mechanism is configured in such a way that the respective deployment side circuits (adjacent terminal) are short-circuited when the connector is disconnected.

Electrical Terminal Fit Detection System

The connectors connected to the SRS unit are equipped with a terminal that short-circuits the fit detection terminals with each other. If the connectors are properly connected, the fit detection terminals are short-circuited to each other, and the SRS unit detects the fitting of the various connectors. If the SRS unit activates when a fitting is not detected, poor terminal fitting is judged and a DTC is stored.

SRS SYSTEM DESCRIPTION - SELECTABLE ENERGY ABSORPTION DEVICE

When the seat belt tensioner operates, it instantly retracts the seat belt, enhancing its ability to immediately restrain the occupant. Also, a selectable energy absorption device is fitted within the front passenger's seat belt tensioner, and this reduces the burden on the occupant's chest while properly maintaining the restraining force of the seat belt. To ensure the seat belt's ability to protect the occupant, the seat belt adjusts to its optimum energy absorption characteristic for the occupant by using the occupant weight information, which is detected by the front passenger's weight sensor.

SRS SYSTEM DESCRIPTION - SIDE AIRBAG AND SIDE CURTAIN AIRBAG

Side Airbag

The side airbags are located at the outside position of the seat-back of the driver's seat and the front passenger's seat. Being installed at the seat-back enables operation in optimal condition for the occupants regardless of the seat slide and recline position.

The side airbag assembly incorporates an inflator and a bag in its casing. It is designed in a way that the airbag tears open the top portion of the airbag casing and the seam of the seat-back to enable efficient deployment. Objects adjacent to deployment or using a seat cover other than the one dedicated for the side airbag may prevent proper operation of the side airbag.

Side Curtain Airbag

A side curtain airbag inflates the full area of the window to protect your head from hitting the window or frame pillar in a side-impact collision. The side curtain airbags are located under the roof side panels.

The side curtain airbags are deployed by triggering a gas inflator located in near the center pillar. Objects adjacent to deployment or attaching parts other than the ones dedicated for side curtain airbags is subject to prevent proper operation of the side curtain airbags.

DTC TROUBLESHOOTING INDEX

SRS DTC TROUBLESHOOTING INDEX (KA/KC)

Front Passenger's Weight Sensor DTC Index

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