DTC C1A4A: Skid Control Buzzer Circuit [11/2017 - 09/2020]: Procedure

1. Check for DTCs of the pre-collision system.

   Body Electrical > Pre-Collision 2 > Trouble Codes 

   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

   Result	Proceed to
   DTC C1A4A is not output	A
   DTC C1A4A is output	B

Result: 

B 

GO TO PRE-COLLISION SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2017 - 10/2022] 

Result: 

A 

See step  2

1. Clear the DTCs.

   Powertrain > Radar Cruise > Clear DTCs 

2. 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 engine switch on (IG).
   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.
3. Check for DTCs.

   Powertrain > Radar Cruise > Trouble Codes 

   Result

   Result	Proceed to
   DTC C1A4A is not output	A
   DTC C1A4A is output	B

Result: 

A 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2017 - 10/2018]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2018 - 11/2019]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2019 - 09/2020] 

Result: 

B 

See step  3

1. Turn the engine switch on (IG).
2. Check that the skid control buzzer assembly sounds.

   Result

   Result	Proceed to
   The skid control buzzer assembly does not sound when the engine switch is on (IG)	A
   The skid control buzzer assembly sounds continuously when the engine switch is on (IG)	B

Result: 

B 

See step  7

Result: 

A 

See step  4

1. Disconnect the O40 skid control buzzer assembly connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Skid Control Buzzer Assembly)

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

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   O40-2 (IG1) - Body ground	Engine switch on (IG)	11 to 14 V
   O40-2 (IG1) - Body ground	Engine switch off	Below 1 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  5

1. Disconnect the O40 skid control buzzer assembly connector.
2. Disconnect the Q2 driving support ECU assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   O40-1 (BZ) - Q2-3 (BZ)	Always	Below 1 Ω
   O40-1 (BZ) or Q2-3 (BZ) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  6

1. Remove the skid control buzzer assembly.

   Refer to REMOVAL [09/2014 - ]

2. Inspect the skid control buzzer assembly.

   Refer to INSPECTION [09/2014 - ]

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  COMPONENTS [09/2014 - 10/2022] 

Result: 

NG 

REPLACE SKID CONTROL BUZZER ASSEMBLY. Refer to  COMPONENTS [09/2014 - 10/2022] 

1. Disconnect the O40 skid control buzzer assembly connector.
2. Disconnect the Q2 driving support ECU assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   O40-1 (BZ) - Q2-3 (BZ)	Always	Below 1 Ω
   O40-1 (BZ) or Q2-3 (BZ) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE DRIVING SUPPORT ECU ASSEMBLY. Refer to  COMPONENTS [09/2014 - 10/2022] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR