Pre-Collision System

PRE-COLLISION: PRE-COLLISION SYSTEM: U0122,U0123,U0126,U0140,U0151,U0235,U1100,U1104: Lost Communication with Vehicle Dynamics Control Module
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-collision 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-collision 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-collision system (DTC U1104).





WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
* When replacing the millimeter wave radar sensor with a new one, make sure to perform Adjust Millimeter Wave Radar Sensor Adjustments.
* Inspect the fuses for circuits related to this system between performing the following inspection procedure.
* Confirm that the connector is securely connected, as a partially connected connector is suspected for the cause of this DTC.

PROCEDURE

1. CHECK FOR DTC

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Pre-Collision and Pre-Collision 2 / Trouble Codes.

(e) Check for DTCs.

Result





B -- GO TO CAN COMMUNICATION SYSTEM How to Proceed With Troubleshooting
A -- Continue to next step.

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

(a) Disconnect the A44 driving support ECU and A36 millimeter wave radar sensor connectors.

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

Standard Resistance:





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

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

3. CHECK MILLIMETER WAVE RADAR SENSOR (IGB VOLTAGE)

(a) Disconnect the A36 millimeter wave radar sensor connector.





(b) Turn the ignition switch to ON.

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

Standard Voltage:





Text in Illustration





(d) Reconnect the millimeter wave radar sensor connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (IGB CIRCUIT)
OK -- Continue to next step.

4. CHECK MILLIMETER WAVE RADAR SENSOR (SGND CIRCUIT)

(a) Disconnect the A36 millimeter wave radar sensor connector.





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

Standard Resistance:





Text in Illustration





(c) Reconnect the millimeter wave radar sensor connector.

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (SGND CIRCUIT)
OK -- Continue to next step.

5. INSPECT DRIVING SUPPORT ECU (LRRD OUTPUT VOLTAGE)

(a) Turn the ignition switch to ON.





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

Standard Voltage:





Text in Illustration





NG -- REPLACE DRIVING SUPPORT ECU Removal
OK -- Continue to next step.

6. REPLACE MILLIMETER WAVE RADAR SENSOR

(a) Replace the millimeter wave radar sensor Removal.

(b) Adjust the millimeter wave radar sensor Adjustments.

NEXT -- Continue to next step.

7. CHECK FOR DTC

(a) Clear the DTCs Pre-Collision System.

(b) Check for DTCs Pre-Collision System.

Result





B -- REPLACE DRIVING SUPPORT ECU Removal

A -- END