C1378

BRAKE CONTROL: ELECTRONICALLY CONTROLLED BRAKE SYSTEM: C1378/44: Capacitor Communication Malfunction

DTC C1378/44 - Capacitor Communication Malfunction

DESCRIPTION

The brake control power supply assembly (capacitor) provides auxiliary power for brake control when an auxiliary battery (12 V) voltage drops.
The FAIL and ENA line are placed between the skid control ECU and the brake control power supply assembly. Signals indicating that the brake control power supply is in auxiliary mode are sent to the skid control ECU through the FAIL line.
Charge permit prohibition signals are sent to the brake control power supply through the ENA line.






WIRING DIAGRAM





INSPECTION PROCEDURE
NOTE: When replacing the skid control ECU, perform initialization of linear solenoid valve and calibration Initialization.

PROCEDURE

1. CHECK BRAKE CONTROL POWER SUPPLY (IG VOLTAGE)




(a) Measure the voltage of the connector.
HINT: Measure the voltage from behind the connector with the connector connected to the skid control ECU.

Standard voltage:






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

2. CHECK WIRE HARNESS (SKID CONTROL ECU - BRAKE CONTROL POWER SUPPLY)




(a) Disconnect the S8 ECU connector.
(b) Disconnect the B18 supply connector.
(c) Measure the resistance of the wire harness side connectors.
Standard resistance:






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

3. CHECK SKID CONTROL ECU (ENA, FAIL VOLTAGE)




(a) Using an oscilloscope, check the waveform of the skid control ECU.
OK:
Waveform is output as shown in the illustration.
Waveform (FAIL):






Waveform (ENA):










C -- REPLACE SKID CONTROL ECU
B -- REPLACE BRAKE CONTROL POWER SUPPLY
A -- REPLACE SKID CONTROL ECU