CAN Communication System

NETWORKING: CAN COMMUNICATION SYSTEM: U0129: Lost Communication with Brake System Control Module
U0129 - Lost Communication with Brake System Control Module

DESCRIPTION





HINT
The diagnosis procedure is for when DTC U0129 is output by the power management control ECU (Techstream display: Power Management1).

WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
* Turn the power switch off before measuring the resistances between CAN bus main wires and between CAN bus branch wires.
* Turn the power switch off before inspecting CAN bus wires for a ground short.
* After the power switch is turned off, check that the key reminder warning system and light reminder warning system are not operating.
* Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the power switch, any other switches or the doors. If any doors need to be opened in order to check connectors, open the doors and leave them open.
HINT
* Operating the power switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.
* Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.
PROCEDURE

1. RECONFIRM DTC OUTPUT

(a) Reconfirm DTCs.

HINT
If power management bus DTC U1002 is output from the power management control ECU (Techstream display/Power Management1), troubleshoot for U1002 and check for malfunctions in the CAN No. 2 main bus circuit.

Result:





B -- GO TO CIRCUITS INDICATED BY OUTPUT DTCS U1002
A -- Continue to next step.

2. CHECK DTC (BRAKE SYSTEM)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Chassis / ABS/VSC/TRAC / Trouble Codes.

OK:

DTC C1241 is not output.

NG -- GO TO CIRCUITS INDICATED BY OUTPUT DTCS C1241
OK -- Continue to next step.

3. CHECK CAN BUS WIRE FOR DISCONNECTION (SKID CONTROL ECU)

(a) Turn the power switch off.

(b) Disconnect the brake booster with master cylinder (skid control ECU) connector.





Text in Illustration





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

Standard Resistance:





NG -- REPAIR OR REPLACE CAN BUS BRANCH WIRE OR CONNECTOR (SKID CONTROL ECU)

OK -- REPLACE BRAKE BOOSTER WITH MASTER CYLINDER (SKID CONTROL ECU) Removal