Toyota Avalon (XX50): SRS Warning Light does not Come ON. SRS Warning Light Remains ON. System Description

SRS Warning Light does not Come ON

DESCRIPTION

The SRS warning light is located in the combination meter assembly.

When the SRS is normal, the SRS warning light comes on for approximately 6 seconds after the engine switch is turned from off to on (IG), and then turns off automatically.

If there is a malfunction in the SRS, the SRS warning light comes on to inform the driver of a problem.

If a malfunction occurs in the airbag ECU assembly, combination meter assembly or wire harness connected to the airbag ECU assembly or combination meter assembly, the SRS warning light turns on.

The SRS is equipped with a voltage-increase circuit (DC-DC converter) in the airbag ECU assembly in case the power source voltage drops.

When the battery voltage drops, the voltage-increase circuit (DC-DC converter) functions to increase the voltage of the SRS to normal voltage.

A malfunction in this circuit is not stored in the airbag ECU assembly. The SRS warning light automatically turns off when the power source voltage returns to normal.

The signal to illuminate the SRS warning light is transmitted from the airbag ECU assembly to the combination meter assembly via CAN communication.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

• After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

  Click here

• Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

(a) Measure the voltage of the battery.

Standard Voltage:

11 to 14 V

NG

INSPECT CHARGING SYSTEM AND BATTERY

OK

(a) Turn the engine switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check that the connector is properly connected to the combination meter assembly.

OK:

The connector is properly connected.

HINT:

If the connector is not properly connected, reconnect the connector and proceed to the next inspection.

(d) Disconnect the connector from the combination meter assembly.

(e) Check that the terminals of the connector are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPAIR OR REPLACE CONNECTOR

OK

(a) Connect the cable to the negative (-) battery terminal.

*a Front view of wire harness connector (to Combination Meter Assembly)

(b) Turn the engine switch on (IG).

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

(d) Turn the engine switch off.

(e) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

NG

REPAIR OR REPLACE WIRE HARNESS

OK

(a) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(b) Connect the connector to the combination meter assembly.

(c) Disconnect the connector from the airbag ECU assembly.

(d) Connect the cable to the negative (-) battery terminal.

(e) Turn the engine switch on (IG) and check the SRS warning light condition.

OK:

After the primary check period, the SRS warning light turns off for approximately 10 seconds and then turns back on.

HINT:

The primary check period is approximately 6 seconds after the engine switch is turned on (IG).

OK

REPLACE AIRBAG ECU ASSEMBLY

NG

REPLACE COMBINATION METER ASSEMBLY

SRS Warning Light Remains ON

DESCRIPTION

The SRS warning light is located in the combination meter assembly.

When the SRS is normal, the SRS warning light comes on for approximately 6 seconds after the engine switch is turned from off to on (IG), and then turns off automatically.

If there is a malfunction in the SRS, the SRS warning light comes on to inform the driver of a problem.

If a malfunction occurs in the airbag ECU assembly, combination meter assembly or wire harness connected to the airbag ECU assembly or combination meter assembly, the SRS warning light comes on.

The SRS is equipped with a voltage-increase circuit (DC-DC converter) in the airbag ECU assembly in case the power source voltage drops.

When the battery voltage drops, the voltage-increase circuit (DC-DC converter) functions to increase the voltage of the SRS to normal voltage. In addition, when the voltage drops, the SRS warning light will illuminate.

A malfunction in this circuit is not stored in the airbag ECU assembly. The SRS warning light automatically turns off when the power source voltage returns to normal.

The signal to illuminate the SRS warning light is transmitted from the airbag ECU assembly to the combination meter assembly via CAN communication.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

• After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

  Click here

• Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

(a) Turn the engine switch on (IG) and check the SRS warning light condition.

HINT:

The primary check is performed for approximately 6 seconds after the engine switch is turned on (IG).

B

GO TO STEP 6

A

(a) Measure the voltage of the battery.

Standard Voltage:

11 to 14 V

NG

INSPECT CHARGING SYSTEM AND BATTERY

OK

(a) Turn the engine switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check that the connector is properly connected to the airbag ECU assembly.

OK:

The connector is properly connected.

HINT:

If the connector is not properly connected, reconnect the connector and proceed to the next inspection.

(d) Disconnect the connector from the airbag ECU assembly.

(e) Check that the terminals of the connector are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPLACE WIRE HARNESS

OK

(a) Connect the cable to the negative (-) battery terminal.

*a Front view of wire harness connector (to Airbag ECU Assembly)

(b) Turn the engine switch on (IG).

(c) Operate all components of the electrical systems (defogger, wipers, headlights, heater blower, etc.).

(d) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

(e) Turn the engine switch off.

(f) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

NG

REPLACE WIRE HARNESS

OK

(a) Turn the engine switch on (IG) and check the SRS warning light condition.

OK:

After the primary check period, the SRS warning light turns off for approximately 10 seconds and then turns back on.

HINT:

The primary check period is approximately 6 seconds after the engine switch is turned on (IG).

OK

REPLACE AIRBAG ECU ASSEMBLY

NG

REPLACE COMBINATION METER ASSEMBLY

(a) Using the Techstream, check if the CAN communication system is functioning normally.

OK:

CAN communication system is functioning normally.

HINT:

Refer to Communication Bus Check in CAN Communication System.

Click here

NG

GO TO CAN COMMUNICATION SYSTEM

OK

(a) Measure the voltage of the battery.

Standard Voltage:

11 to 14 V

NG

INSPECT CHARGING SYSTEM AND BATTERY

OK

(a) Turn the engine switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(c) Check that the connector is properly connected to the airbag ECU assembly.

OK:

The connector is properly connected.

HINT:

If the connector is not properly connected, reconnect the connector and proceed to the next inspection.

(d) Disconnect the connector from the airbag ECU assembly.

(e) Check that the terminals of the connector are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPLACE WIRE HARNESS

OK

(a) Connect the cable to the negative (-) battery terminal.

*a Front view of wire harness connector (to Airbag ECU Assembly)

(b) Turn the engine switch on (IG).

(c) Operate all components of the electrical systems (defogger, wipers, headlights, heater blower, etc.).

(d) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

(e) Turn the engine switch off.

(f) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

NG

REPLACE WIRE HARNESS

OK

(a) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(b) Check that the connector is properly connected to the combination meter assembly.

OK:

The connector is properly connected.

HINT:

If the connector is not properly connected, reconnect the connector and proceed to the next inspection.

(c) Disconnect the connector from the combination meter assembly.

(d) Check that the terminals of the connector are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPAIR OR REPLACE CONNECTOR

OK

(a) Connect the cable to the negative (-) battery terminal.

*a Front view of wire harness connector (to Combination Meter Assembly)

(b) Turn the engine switch on (IG).

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

(d) Turn the engine switch off.

(e) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

NG

REPAIR OR REPLACE WIRE HARNESS

OK

(a) Disconnect the cable from the negative (-) battery terminal.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

(b) Connect the connector to the combination meter assembly.

(c) Connect the cable to the negative (-) battery terminal.

(d) Turn the engine switch on (IG) and check the SRS warning light condition.

OK:

After the primary check period, the SRS warning light turns off for approximately 10 seconds and then turns back on.

HINT:

The primary check period is approximately 6 seconds after the engine switch is turned on (IG).

OK

REPLACE AIRBAG ECU ASSEMBLY

NG

REPLACE COMBINATION METER ASSEMBLY

System Description

SYSTEM DESCRIPTION

FUNCTION OF SRS CONNECTORS

(a) Location of activation prevention mechanism

(b) Function of activation prevention mechanism

(1) This mechanism is designed to create a short circuit automatically between the positive (+) and negative (-) terminals of a squib power source connector when disconnected.

(2) The short spring contained in the connector creates a closed circuit on the squib side (no potential difference can occur between both terminals), preventing accidental squib deployment when servicing.

(c) Releasing of activation prevention mechanism

(1) To release the activation prevention mechanism, insert a piece of paper with the same thickness as the male terminal (approximately 0.5 mm (0.0197 in.)) between the terminals and short spring to break the connection.

(2) Refer to the following illustrations concerning connectors utilizing the activation prevention mechanism and its release method.

CAUTION:

Never release the activation prevention mechanism on the squib connector even when inspecting with the squib disconnected.

NOTICE:

• Do not release the activation prevention mechanism unless specified by the troubleshooting procedure.
• To prevent the terminals and short spring from being damaged, always use a piece of paper with the same thickness as the male terminal.

HINT:

To prevent improper operation due to static electricity, etc., the connector of the airbag and pretensioner squib circuit has a short mechanism, and the squib terminal is shorted while the connector is disconnected.