PRE-CRASH SAFETY SYSTEM, Diagnostic DTC:U0122, U0123, U0126, U0140, U0151, U0293, U1100, U1104

DTC Code	DTC Name
U0122	Lost Communication with Vehicle Dynamics Control Module
U0123	Communication Error of Yaw Rate Sensor
U0126	Lost Communication with Steering Angle Sensor Module
U0140	Lost Communication with Main Body ECU
U0151	Lost Communication with Airbag ECU
U0293	Lost Communication with HV ECU
U1100	Lost Communication with Seat Belt Control ECU
U1104	Lost Communication with Driving Support ECU

DESCRIPTION

The driving support ECU uses the millimeter wave radar sensor to detect obstacles in front of the vehicle. Based on this information, the driving support ECU sends pre-crash control operation signals. These DTCs are stored when a communication malfunction occurs between the sensors and ECUs that detect collisions, or between ECUs that perform the pre-crash control.
The driving support ECU sends vehicle speed and vehicle condition information to the millimeter wave radar sensor. The millimeter wave radar sensor then sends information on the presence, distance, and relative speed of objects ahead to the driving support ECU. The driving support ECU sends this information to the ECM and performs pre-crash safety system (DTC U1104).

DTC No.	DTC Detection Condition	Trouble Area
U0122	When the power switch is on (IG), a communication error between the skid control ECU assembly and the driving support ECU is detected for approx. 1 second. When the power switch is on (IG), a communication error between the skid control ECU assembly and the seat belt control ECU is detected for approx. 1 second.	Skid control ECU assembly CAN communication system Seat belt control ECU Driving support ECU
U0123	When the power switch is on (IG), a communication error between the yaw rate sensor and the driving support ECU is detected for approx. 1 second.	Yaw rate sensor CAN communication system Driving support ECU
U0126	When the power switch is on (IG), a communication error between the steering angle sensor and the driving support ECU is detected for approx. 1 second.	Steering angle sensor CAN communication system Driving support ECU
U0140	While power switch is on (IG), communication stop between main body ECU and seat belt control ECU continues for 1 second or more.	Main body ECU CAN communication system Seat belt control ECU
U0151	While power switch is on (IG), communication stop between center airbag sensor and seat belt control ECU continues for 1 second or more.	Center airbag sensor CAN communication system Seat belt control ECU
U0293	When the power switch is on (IG), a communication error between the power management control ECU and skid control ECU assembly is detected for approx. 1 second. When the power switch is on (IG), a communication error between the power management control ECU and driving support ECU is detected for approx. 1 second.	Power management control ECU Skid control ECU assembly CAN communication system Driving support ECU
U1100	When the power switch is on (IG), a communication error between the seat belt control ECU and the driving support ECU is detected for approx. 1 second.	Seat belt control ECU CAN communication system Driving support ECU
U1104	When the power switch is on (IG), a communication error between the driving support ECU and the millimeter wave radar sensor is detected for approx. 1 second. When the power switch is on (IG), a communication error between the driving support ECU and the power management control ECU is detected for approx. 1 second.	Communication circuit Millimeter wave radar sensor Driving support ECU Power management control ECU CAN communication system

WIRING DIAGRAM

INSPECTION PROCEDURE

Note

When replacing the millimeter wave radar sensor with a new one, make sure to perform Adjust Millimeter Wave Radar Sensor Assembly Click here.
Confirm that the connector is securely connected, as a partially connected connector is suspected for the cause of this DTC.

PROCEDURE

CHECK CAN COMMUNICATION SYSTEM

Select "CAN Bus Check" from the "System Selection Menu" screen on the intelligent tester.

Select "Communication Malfunction DTC" from the "CAN Bus Check" screen, and then select "Enter".

Result

Result	Proceed to
DTC U1104 is not output	A
DTC U1104 is output	B

CHECK HARNESS AND CONNECTOR (DRIVING SUPPORT ECU - MILLIMETER WAVE RADAR SENSOR) Click here

GO TO CAN COMMUNICATION SYSTEM Click here

CHECK HARNESS AND CONNECTOR (DRIVING SUPPORT ECU - MILLIMETER WAVE RADAR SENSOR)

Text in Illustration
*1	Front view of wire harness connector (to Millimeter Wave Radar Sensor)
*2	Front view of wire harness connector (to Driving Support ECU)

Disconnect the driving support ECU and millimeter wave radar sensor connectors.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
C1-38 (LRRD) - B1-4 (LRRD)	Always	Below 1 Ω
B1-4 (LRRD) - Body ground	Always	10 kΩ or higher
C1-38 (LRRD) - Body ground	Always	10 kΩ or higher

Reconnect the driving support ECU and millimeter wave radar sensor connectors.

REPAIR OR REPLACE HARNESS OR CONNECTOR (DRIVING SUPPORT ECU - MILLIMETER WAVE RADAR SENSOR)

CHECK MILLIMETER WAVE RADAR SENSOR (IGB VOLTAGE)

Text in Illustration

*1
Front view of wire harness connector

(to Millimeter Wave Radar Sensor)

Disconnect the millimeter wave radar sensor connector.
Turn the power switch on (IG).

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

Standard Voltage

Tester Connection	Condition	Specified Condition
B1-5 (IGB) - Body ground	Power switch on (IG)	11 to 14 V

Reconnect the millimeter wave radar sensor connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (IGB CIRCUIT)

CHECK MILLIMETER WAVE RADAR SENSOR (SGND CIRCUIT)

Text in Illustration

*1
Front view of wire harness connector

(to Millimeter Wave Radar Sensor)

Disconnect the millimeter wave radar sensor connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
B1-2 (SGND) - Body ground	Always	Below 1 Ω

Reconnect the millimeter wave radar sensor connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (SGND CIRCUIT)

CHECK DRIVING SUPPORT ECU (LRRD OUTPUT VOLTAGE)

Text in Illustration

*1
Component with harness connected

(Driving Support ECU)

Turn the power switch on (IG).

Text in Illustration
*1	Component with harness connected (Driving Support ECU)

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

Standard Voltage

Tester Connection	Condition	Specified Condition
C1-38 (LRRD) - Body ground	Power switch on (IG)	4.5 to 5.5 V

REPLACE DRIVING SUPPORT ECU Click here

REPLACE MILLIMETER WAVE RADAR SENSOR
1. Replace the millimeter wave radar sensor Click here.
2. Adjust the millimeter wave radar sensor Click here.
NEXT

CHECK DTC OUTPUT

Clear the DTCs Click here.
Turn the cruise control main switch on.
Drive the vehicle at the required speed (45 km/h (27 mph) or higher).

Check if the same DTC is output Click here.

Result

Result	Proceed to
DTC U1104 is not output	A
DTC U1104 is output	B

REPLACE MILLIMETER WAVE RADAR SENSOR Click here

END