Last Modified: 04-05-2023 6.11:8.1.0 Doc ID: RM1000000018WSB
Model Year Start: 2018 Model: Sienna Prod Date Range: [11/2017 -           ]
Title: CRUISE CONTROL: DYNAMIC RADAR CRUISE CONTROL SYSTEM: C1A4A; Skid Control Buzzer Circuit; 2018 - 2020 MY Sienna [11/2017 -        ]

DTC

C1A4A

Skid Control Buzzer Circuit

DESCRIPTION

Based on dynamic radar cruise control system operation, the driving support ECU assembly provides warnings to the driver by sounding the skid control buzzer assembly.

DTC C1A4A is stored when a malfunction is detected in the skid control buzzer circuit.

DTC No.

DTC Detection Condition

Trouble Area

MIL

C1A4A

While the vehicle speed is 36 km/h (22 mph) or more and the dynamic radar cruise control system is operating, the driving support ECU assembly detects a malfunction in the skid control buzzer circuit for approximately 0.4 seconds or more.
  • Skid control buzzer assembly
  • Millimeter wave radar sensor assembly
  • Driving support ECU assembly
  • Harness or connector

Does not come on

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • When replacing the driving support ECU assembly, make sure to replace it with a new one. If a device which was installed to another vehicle is used, the information stored in the driving support ECU assembly will not match the information from the vehicle, and as a result, a DTC may be stored.
  • First check the CAN communication system by following How to Proceed with Troubleshooting. After checking that there are no malfunctions in the CAN communication system, proceed with troubleshooting.

    Click here 2018 - 2020 MY Sienna [11/2017 -        ]; CRUISE CONTROL: MILLIMETER WAVE RADAR SENSOR: ADJUSTMENT

PROCEDURE

1.

CHECK FOR DTCs (PRE-COLLISION SYSTEM)

(a) Check for DTCs of the pre-collision system.

Click here 2018 - 2020 MY Sienna [11/2017 -        ]; PRE-COLLISION: PRE-COLLISION SYSTEM: DTC CHECK / CLEAR

HINT:

The dynamic radar cruise control system only stores DTC C1A4A when the vehicle speed reaches 36 km/h (22 mph), however the pre-collision system stores this DTC at any vehicle speed. If DTC C1A4A is stored by the pre-collision system, perform troubleshooting of the pre-collision system first.

Result

Proceed to

DTC C1A4A is not output

A

DTC C1A4A is output

B
B

GO TO PRE-COLLISION SYSTEM

A

2.

CHECK FOR DTCs (RADAR CRUISE 2)

(a) Clear the DTCs.

Click here 2018 - 2020 MY Sienna [11/2017 -        ]; CRUISE CONTROL: DYNAMIC RADAR CRUISE CONTROL SYSTEM: DTC CHECK / CLEAR

(b) Perform the following to make sure that the DTC detection conditions are met.

HINT:

If the following conditions are not met, the system cannot detect the malfunction.

  1. Turn the ignition switch to ON.
  2. Turn the dynamic radar cruise control system on using the cruise control main switch (ON-OFF button).
  3. Drive the vehicle at 36 km/h (22 mph) or more for 1 second or more.

(c) Check for DTCs.

Click here 2018 - 2020 MY Sienna [11/2017 -        ]; CRUISE CONTROL: DYNAMIC RADAR CRUISE CONTROL SYSTEM: DTC CHECK / CLEAR

Result

Proceed to

DTC C1A4A is not output

A

DTC C1A4A is output

B
A

USE SIMULATION METHOD TO CHECK

B

3.

INSPECT SKID CONTROL BUZZER ASSEMBLY (CONFIRM BUZZER OPERATION)

(a) Turn the ignition switch to ON.

(b) Check that the skid control buzzer assembly sounds.

Result

Proceed to

The skid control buzzer assembly does not sound when the ignition switch is ON.

A

The skid control buzzer assembly sounds continuously when the ignition switch is ON.

B
B

GO TO STEP 7

A

4.

CHECK HARNESS AND CONNECTOR (SKID CONTROL BUZZER ASSEMBLY - BATTERY)

(a) Disconnect the skid control buzzer assembly connector.

*a

Front view of wire harness connector

(to Skid Control Buzzer Assembly)

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

A21-2 (IG1) - Body ground

Ignition switch ON

11 to 14 V

A21-2 (IG1) - Body ground

Ignition switch off

Below 1 V

Proceed to

OK

NG
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

CHECK HARNESS AND CONNECTOR (SKID CONTROL BUZZER ASSEMBLY - DRIVING SUPPORT ECU ASSEMBLY)

(a) Disconnect the A21 skid control buzzer assembly connector.

(b) Disconnect the A80 driving support ECU assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A21-1 (BZ) - A80-3 (BZ)

Always

Below 1 Ω

A21-1 (BZ) or A80-3 (BZ) - Body ground

Always

10 kΩ or higher

Proceed to

OK

NG
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

6.

INSPECT SKID CONTROL BUZZER ASSEMBLY

(a) Remove the skid control buzzer assembly.

Click here 2016 - 2020 MY Sienna [12/2015 -        ]; BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: SKID CONTROL BUZZER: REMOVAL

(b) Inspect the skid control buzzer assembly.

Click here 2016 - 2020 MY Sienna [12/2015 -        ]; BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: SKID CONTROL BUZZER: INSPECTION

Proceed to

OK

NG
OK

REPLACE DRIVING SUPPORT ECU ASSEMBLY

NG

REPLACE SKID CONTROL BUZZER ASSEMBLY

7.

CHECK HARNESS AND CONNECTOR (SKID CONTROL BUZZER ASSEMBLY - DRIVING SUPPORT ECU ASSEMBLY)

(a) Disconnect the A21 skid control buzzer assembly connector.

(b) Disconnect the A80 driving support ECU assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A21-1 (BZ) - A80-3 (BZ)

Always

Below 1 Ω

A21-1 (BZ) or A80-3 (BZ) - Body ground

Always

10 kΩ or higher

Proceed to

OK

NG
OK

REPLACE DRIVING SUPPORT ECU ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR