Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: LO-beam Headlight does not Illuminate

DESCRIPTION

The main body ECU (multiplex network body ECU) controls the low beam headlights.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Before replacing the main body ECU (multiplex network body ECU), refer to Registration.

    Click here

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM

(a) Connect the Techstream to the DLC3.

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

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Main Body / Active Test.

(e) Perform the Active Test according to the display on the Techstream.

Body Electrical > Main Body > Active Test

Tester Display

Measurement Item

Control Range

Diagnostic Note

Headlight Relay

Low beam headlights

OFF or ON

-

Body Electrical > Main Body > Active Test

Tester Display

Headlight Relay

OK:

Low beam headlights illuminate.

Result

Proceed to

OK

A

NG (for LH Side)

B

NG (for RH Side)

C

A

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE

C

GO TO STEP 9

B

2.

INSPECT HEADLIGHT ASSEMBLY LH (LO TERMINAL VOLTAGE)

*a

Front view of wire harness connector

(to Headlight Assembly LH)

(a) Disconnect the A45 headlight assembly LH connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A45-4 (LO) - Body ground

Light control switch in head position

11 to 14 V

NG

GO TO STEP 4

OK

3.

CHECK HARNESS AND CONNECTOR (HEADLIGHT ASSEMBLY LH - BODY GROUND)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A45-7 (E) - Body ground

Always

Below 1 Ω

OK

REPLACE HEADLIGHT ASSEMBLY LH

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.

CHECK HARNESS AND CONNECTOR (H-LP LH RELAY - HEADLIGHT ASSEMBLY LH)

(a) Remove the H-LP LH relay.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

5 (H-LP LH relay) - A45-4 (LO)

Always

Below 1 Ω

5 (H-LP LH relay) or A45-4 (LO) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5.

INSPECT H-LP LH RELAY

(a) Inspect the H-LP LH relay.

Click here

NG

REPLACE H-LP LH RELAY

OK

6.

CHECK HARNESS AND CONNECTOR (POWER SOURCE - H-LP LH RELAY)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

1 (H-LP LH relay) - Body ground

Power switch off

11 to 14 V

3 (H-LP LH relay) - Body ground

Power switch off

11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

7.

CHECK HARNESS AND CONNECTOR (H-LP LH RELAY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

(a) Disconnect the 4F instrument panel junction block assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2 (H-LP LH relay) - 4F-31

Always

Below 1 Ω

2 (H-LP LH relay) or 4F-31 - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

8.

INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

*a

Component without harness connected

(Instrument Panel Junction Block Assembly)

-

-

(a) Remove the main body ECU (multiplex network body ECU) from the instrument panel junction block assembly.

Click here

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

4F-31 - MB-15 (HRLY)

Always

Below 1 Ω

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

9.

INSPECT HEADLIGHT ASSEMBLY RH (LO TERMINAL VOLTAGE)

*a

Front view of wire harness connector

(to Headlight Assembly RH)

(a) Disconnect the A44 headlight assembly RH connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A44-4 (LO) - Body ground

Light control switch in head position

11 to 14 V

NG

GO TO STEP 11

OK

10.

CHECK HARNESS AND CONNECTOR (HEADLIGHT ASSEMBLY RH - BODY GROUND)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A44-7 (E) - Body ground

Always

Below 1 Ω

OK

REPLACE HEADLIGHT ASSEMBLY RH

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

11.

CHECK HARNESS AND CONNECTOR (H-LP RH RELAY - HEADLIGHT ASSEMBLY RH)

(a) Remove the H-LP RH relay.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

5 (H-LP RH relay) - A44-4 (LO)

Always

Below 1 Ω

5 (H-LP RH relay) or A44-4 (LO) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

12.

INSPECT H-LP RH RELAY

(a) Inspect the H-LP RH relay.

Click here

NG

REPLACE H-LP RH RELAY

OK

13.

CHECK HARNESS AND CONNECTOR (POWER SOURCE - H-LP RH RELAY)

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

1 (H-LP RH relay) - Body ground

Power switch off

11 to 14 V

3 (H-LP RH relay) - Body ground

Power switch off

11 to 14 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

14.

CHECK HARNESS AND CONNECTOR (H-LP RH RELAY - MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU))

(a) Disconnect the G33 main body ECU (multiplex network body ECU) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2 (H-LP RH relay) - G33-12 (HRY2)

Always

Below 1 Ω

2 (H-LP RH relay) or G33-12 (HRY2) - Body ground

Always

10 kΩ or higher

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

    How To Proceed With Troubleshooting

    Operation Check

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