Last Modified: 04-05-2023 6.11:8.1.0 Doc ID: RM1000000018KF8
Model Year Start: 2018 Model: Sienna Prod Date Range: [11/2017 -           ]
Title: BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: Brake Warning Light Remains ON; 2018 - 2020 MY Sienna [11/2017 -        ]

Brake Warning Light Remains ON

DESCRIPTION

The skid control ECU (brake actuator assembly) is connected to the combination meter assembly via CAN communication.

If any of the following is detected, the brake warning light remains on:

  • The skid control ECU (brake actuator assembly) connector is disconnected from the skid control ECU (brake actuator assembly).
  • The brake fluid level is insufficient.
  • EBD operation is not possible.
  • The vacuum inside the brake booster decreases.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When replacing the skid control ECU (brake actuator assembly), perform zero point calibration and store system information (See page 2018 - 2020 MY Sienna [11/2017 -        ]; BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: CALIBRATION ).
  • If the main body ECU (multiplex network body ECU) is replaced, refer to Registration.
    • w/ Smart Key System:

      (See page 2017 - 2020 MY Sienna [08/2016 -        ]; THEFT DETERRENT / KEYLESS ENTRY: ENGINE IMMOBILISER SYSTEM(w/ Smart Key System): REGISTRATION ).

    • w/o Smart Key System:

      (See page 2016 - 2020 MY Sienna [12/2015 -        ]; THEFT DETERRENT / KEYLESS ENTRY: ENGINE IMMOBILISER SYSTEM(w/o Smart Key System): REGISTRATION ).

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

PROCEDURE

1.

CHECK CAN COMMUNICATION SYSTEM

(a) Check if CAN communication system DTCs are output (See page 2018 MY Sienna [11/2017 - 08/2018]; NETWORKING: CAN COMMUNICATION SYSTEM: DIAGNOSIS SYSTEM 2019 - 2020 MY Sienna [08/2018 -        ]; NETWORKING: CAN COMMUNICATION SYSTEM: DIAGNOSIS SYSTEM ).

Result

Proceed to

DTCs are not output.

A

DTCs are output.

B
B

INSPECT CAN COMMUNICATION SYSTEM

A

2.

CHECK IF BRAKE ACTUATOR ASSEMBLY CONNECTOR IS SECURELY CONNECTED

(a) Check if the skid control ECU (brake actuator assembly) connector is securely connected.

OK:

The connector is securely connected.

NG

CONNECT CONNECTOR TO BRAKE ACTUATOR ASSEMBLY CORRECTLY
OK

3.

INSPECT BATTERY POSITIVE TERMINAL

(a) Check the battery voltage.

Standard Voltage:

11 to 14 V

NG

CHECK OR REPLACE CHARGING SYSTEM OR BATTERY

OK

4.

CHECK HARNESS AND CONNECTOR (IG1 TERMINAL)

(a) Disconnect the skid control ECU (brake actuator assembly) connector.

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

A75-12 (IG1) - Body ground

Ignition switch ON

10.5 to 16 V

Text in Illustration

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Actuator Assembly))
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 CIRCUIT)
OK

5.

CHECK HARNESS AND CONNECTOR (GND1 TERMINAL)

(a) Turn the ignition switch off.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A75-25 (GND1) - Body ground

Always

Below 1 Ω

Text in Illustration

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Actuator Assembly))
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND1 CIRCUIT)
OK

6.

READ VALUE USING TECHSTREAM (PARKING BRAKE SWITCH ASSEMBLY)

(a) Reconnect the A75 skid control ECU (brake actuator assembly) connector.

(b) Connect the Techstream to the DLC3.

(c) Turn the ignition switch to ON.

(d) Turn the Techstream on.

(e) Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

(f) Select the Data List using the Techstream (See page 2018 - 2020 MY Sienna [11/2017 -        ]; BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: DATA LIST / ACTIVE TEST ).

ABS/VSC/TRAC

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Parking Brake SW

Parking brake switch assembly / ON or OFF

ON: Parking brake applied

OFF: Parking brake released

-

(g) Using the Techstream, check the switch operation signal received when the parking brake is operated.

OK:

When the parking brake is operated, the display changes as shown above.

NG

GO TO STEP 11

OK

7.

INSPECT BRAKE FLUID LEVEL WARNING SWITCH (BRAKE MASTER CYLINDER RESERVOIR SUB-ASSEMBLY)

(a) Turn the ignition switch off.

(b) Remove the reservoir filler cap and strainer.

(c) Disconnect the A30 brake fluid level warning switch (brake master cylinder reservoir sub-assembly) connector.

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

HINT:

A float is located inside the reservoir. Its position can be changed by increasing or decreasing the level of brake fluid.

Standard Resistance:

Tester Connection

Condition

Specified Condition

A30-1 (+) - A30-2 (E)

Switch off (Float up)

1.9 to 2.1 kΩ

A30-1 (+) - A30-2 (E)

Switch on (Float down)

Below 1 Ω

Text in Illustration

*a

Component without harness connected

(Brake Fluid Level Warning Switch (Brake Master Cylinder Reservoir Sub-assembly))

HINT:

If there is no problem after finishing the above check, adjust the brake fluid level to the MAX level.

NG

REPLACE BRAKE FLUID LEVEL WARNING SWITCH (BRAKE MASTER CYLINDER RESERVOIR SUB-ASSEMBLY)

OK

8.

INSPECT VACUUM WARNING SWITCH ASSEMBLY

(a) Inspect the vacuum warning switch assembly (See page 2017 - 2020 MY Sienna [08/2016 -        ]; BRAKE SYSTEM (OTHER): VACUUM WARNING SWITCH: ON-VEHICLE INSPECTION ).

OK:

The vacuum warning switch assembly is normal.

NG

REPLACE VACUUM WARNING SWITCH ASSEMBLY

OK

9.

CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - BRAKE MASTER CYLINDER RESERVOIR ASSEMBLY)

(a) Disconnect the D145 combination meter assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

D145-9 (B/LE) - A30-1 (+)

Always

Below 1 Ω

D145-9 (B/LE) - Body ground

Always

10 kΩ or higher

A30-2 (E) - Body ground

Always

Below 1 Ω

D145-9 (B/LE) - A68-2 (+)

Always

Below 1 Ω

A68-1 (E) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

10.

READ VALUE USING TECHSTREAM (BRAKE WARNING LIGHT)

(a) Reinstall the reservoir filler cap and strainer.

(b) Reconnect the D145 combination meter assembly connector and the A26 brake fluid level warning switch (brake master cylinder reservoir assembly) connector.

(c) Reconnect the A75 skid control ECU (brake actuator assembly) connector.

(d) Connect the Techstream to the DLC3.

(e) Turn the ignition switch to ON.

(f) Turn the Techstream on.

(g) Enter the following menus: Body Electrical / Combination Meter / Active Test.

(h) Select the Data List using the Techstream (See page 2018 - 2020 MY Sienna [11/2017 -        ]; BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: DATA LIST / ACTIVE TEST ).

ABS/VSC/TRAC

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Brake Warning Light

Brake warning light / ON or OFF

ON: Warning light on

OFF: Warning light off

-

(i) Check the Techstream display condition of the brake warning light.

Result

Proceed to

Display of the Data List remains ON.

A

Display of the Data List remains OFF.

B

HINT:

If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step before replacing parts (See page 2018 - 2020 MY Sienna [11/2017 -        ]; BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: PROBLEM SYMPTOMS TABLE ).

A

REPLACE BRAKE ACTUATOR ASSEMBLY

B

INSPECT METER / GAUGE SYSTEM

11.

INSPECT PARKING BRAKE SWITCH ASSEMBLY

(a) Turn the ignition switch off.

(b) Disconnect the A3 parking brake switch assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

1 - Body ground

Parking brake switch on

(Switch pin free)

Below 1 Ω

1 - Body ground

Parking brake switch off

(Switch pin pushed in)

10 kΩ or higher

Text in Illustration

*a

Component without harness connected

(Parking Brake Switch Assembly)
NG

REPLACE PARKING BRAKE SWITCH ASSEMBLY

OK

12.

CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - PARKING BRAKE SWITCH)

(a) Disconnect the 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

2F-22 - A3-1

Always

Below 1 Ω

2F-22 - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

13.

CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - MAIN BODY ECU)

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

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

2I-12 - 2F-22

Always

Below 1 Ω

2I-12 - Body ground

Always

10 kΩ or higher

HINT:

If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step before replacing the part (See page 2018 - 2020 MY Sienna [11/2017 -        ]; BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: VEHICLE STABILITY CONTROL SYSTEM: PROBLEM SYMPTOMS TABLE ).

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY