Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: Short in D Squib Circuit (B1800-B1803)

DESCRIPTION

The driver squib circuit consists of the airbag ECU assembly, spiral cable sub-assembly and horn button assembly.

The airbag ECU assembly uses this circuit to deploy the airbag when deployment conditions are met.

These DTCs are stored when a malfunction is detected in the driver squib circuit.

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.

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HINT:

• Perform the simulation method by selecting check mode (Signal Check) using the Techstream.

  Click here

• After selecting check mode (Signal Check), perform the simulation method by wiggling each connector of the airbag system or driving the vehicle on a city road or rough road.

  Click here

PROCEDURE

(a) Turn the engine switch off.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag ECU Assembly *4 Instrument Panel Wire

(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 connectors are properly connected to the horn button assembly, spiral cable sub-assembly and airbag ECU assembly.

OK:

The connectors are properly connected.

HINT:

If the connectors are not properly connected, reconnect the connectors and proceed to the next inspection.

(d) Disconnect the connectors from the horn button assembly, spiral cable sub-assembly and airbag ECU assembly.

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

OK:

The terminals are not deformed or damaged.

(f) Check that the spiral cable sub-assembly connector (on the horn button assembly side) is not loose, deformed or damaged.

OK:

The airbag connector locking button is not disengaged, and the claw of the lock is not deformed or damaged.

(g) Check that the short springs of the activation prevention mechanisms of the instrument panel wire connector and spiral cable sub-assembly connector are not deformed or damaged.

OK:

The short springs are not deformed or damaged.

NG

REPLACE WIRE HARNESS

OK

(a) Connect the instrument panel wire to the airbag ECU assembly and spiral cable sub-assembly.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag ECU Assembly *a Front view of wire harness connector (to Horn Button Assembly) *b Color: Light Green

(b) Connect SST (resistance 2.1 Ω) to connector E (light green connector).

CAUTION:

Never connect a tester to the horn button assembly for measurement, as this may lead to a serious injury due to airbag deployment.

NOTICE:

• Do not forcibly insert SST into the terminals of the connector when connecting it.
• Insert SST straight into the terminals of the connector.

SST: 09843-18061

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

(d) Turn the engine switch on (IG), and wait for at least 60 seconds.

(e) Clear the DTCs stored in memory.

(f) Turn the engine switch off.

(g) Turn the engine switch on (IG), and wait for at least 60 seconds.

(h) Check for DTCs.

OK:

DTC B1800, B1801, B1802 or B1803 is not output.

HINT:

Codes other than DTCs B1800, B1801, B1802 and B1803 may be output at this time, but they are not related to this check.

(i) Turn the engine switch off.

(j) 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.

(k) Disconnect SST from connector E.

OK

REPLACE HORN BUTTON ASSEMBLY

NG

(a) Disconnect the instrument panel wire from the airbag ECU assembly.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag ECU Assembly *a Front view of wire harness connector (to Horn Button Assembly) *b Color: Light Green

(b) Check for a short to B+ in the circuit.

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

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

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

Standard Voltage:

(4) Turn the engine switch off.

(5) 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 for an open in the circuit.

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

Standard Resistance:

(d) Check for a short to ground in the circuit.

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

Standard Resistance:

(e) Check for a short in the circuit.

(1) Release the activation prevention mechanism built into connector B.

Click here

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

Standard Resistance:

(3) Restore the released activation prevention mechanism of connector B to the original condition.

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GO TO STEP 5

OK

(a) Connect the connectors to the horn button assembly and airbag ECU assembly.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag ECU Assembly

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

(c) Turn the engine switch on (IG), and wait for at least 60 seconds.

(d) Clear the DTCs stored in memory.

(e) Turn the engine switch off.

(f) Turn the engine switch on (IG), and wait for at least 60 seconds.

(g) Check for DTCs.

OK:

DTC B1800, B1801, B1802 or B1803 is not output.

HINT:

Codes other than DTCs B1800, B1801, B1802 and B1803 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE AIRBAG ECU ASSEMBLY

(a) Disconnect the instrument panel wire from the spiral cable sub-assembly.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag ECU Assembly *4 Instrument Panel Wire *a Front view of wire harness connector (to Spiral Cable Sub-assembly)

(b) Check for a short to B+ in the circuit.

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

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

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

Standard Voltage:

(4) Turn the engine switch off.

(5) 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 for an open in the circuit.

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

Standard Resistance:

(d) Check for a short to ground in the circuit.

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

Standard Resistance:

(e) Check for a short in the circuit.

(1) Release the activation prevention mechanism built into connector B.

Click here

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

Standard Resistance:

(3) Restore the released activation prevention mechanism of connector B to the original condition.

NG

REPLACE INSTRUMENT PANEL WIRE

OK

(a) Check for a short to B+ in the circuit. (1) Connect the cable to the negative (-) battery terminal. (2) Turn the engine switch on (IG). (3) Measure the voltage according to the value(s) in the table below. Standard Voltage: Tester Connection Condition Specified Condition z5-2 (D+) - Body ground Engine switch on (IG) Below 1 V z5-1 (D-) - Body ground Engine switch on (IG) Below 1 V (4) Turn the engine switch off. (5) 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.

*1 Horn Button Assembly *2 Spiral Cable Sub-assembly *3 Airbag ECU Assembly *4 Instrument Panel Wire *a Front view of wire harness connector (to Horn Button Assembly) *b Color: Light Green

(b) Check for an open in the circuit.

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

Standard Resistance:

(c) Check for a short to ground in the circuit.

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

Standard Resistance:

(d) Check for a short in the circuit.

(1) Release the activation prevention mechanism built into connector D.

Click here

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

Standard Resistance:

(3) Restore the released activation prevention mechanism of connector D to the original condition.

OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE SPIRAL CABLE SUB-ASSEMBLY