DTC P0C78: Hybrid Battery System PRECHARGE Time Too Long: Wiring Diagram

WARNING: This page is about a different car, the 2015 Subaru XV Crosstrek. However, it is still accessible from the selected car via links, so may be relevant.

Hybrid system < Ref. to WIRING DIAGRAM , Hybrid Electric Vehicle System.>

Fig 1: Hybrid Battery System Precharge Time Too Long - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DTC PROCEDURE

Step	Check	Yes	No
1 CHECK DTC. Using the Subaru Select Monitor, read DTCs of the following system. Drive motor control system < Ref. to DRIVE MOTOR CONTROL SYSTEM , OPERATION, Read Diagnostic Trouble Code (DTC).>	Are any other DTCs detected? (current malfunction)	Perform the diagnosis according to DTC. < Ref. to DRIVE MOTOR CONTROL SYSTEM , LIST, List of Diagnostic Trouble Code (DTC).>	Go to step 2 .
2 CHECK CURRENT DATA. Using the Subaru Select Monitor, confirm the current data of battery energy control system, the value of «High voltage Battery Total Voltage ». < Ref. to BATTERY ENERGY CONTROL SYSTEM , OPERATION, Read Current Data.>	Is the value 75 V or more?	Go to step 3 .	Replace the high voltage battery. < Ref. to HIGH VOLTAGE BATTERY .>
3 CHECK DRIVE MOTOR. With the 12 V battery connected, remove the service disconnect plug. < Ref. to SERVICE PLUG .> CAUTION: Watch for an electrical short at each harness because the 12 V battery is connected. Lift up the vehicle. Start the engine, and set the shift lever to "D" range. Using the Subaru Select Monitor, confirm the current data of battery energy control system, the values of «Drive Motor Speed»«Drive Motor Inverter Input Voltage». < Ref. to BATTERY ENERGY CONTROL SYSTEM , OPERATION, Read Current Data.> NOTE: When current data of the drive motor control system, «ATF Temperature» is 20 - 60°C (68 - 140°F). < Ref. to DRIVE MOTOR CONTROL SYSTEM , OPERATION, Read Current Data.>	Is «Drive Motor Inverter Input Voltage» within the standard in the margin when «Drive Motor Speed» is 600 - 1400 rpm?	Go to step 4 .	Replace the drive motor inverter. < Ref. to INVERTER .>
4 CHECK BUS BAR. Turn the ignition to OFF. Disconnect the ground cable of the 12 volt auxiliary battery, and as for the 12 volt engine restart battery, disconnect the ground cable from the 12V engine restart battery sensor. < Ref. to BATTERY , NOTE, Note.> Remove the service disconnect plug. Wait for 10 minutes. Check the bus bar.	Is the condition normal? (Check for loose bolts, insecure connection, foreign matter caught, trace of arc (burnt terminals) etc.)	Go to step 5 .	Retighten the bolts. Or replace the bus bar.
5 CHECK BUS BAR. Remove the bus bar. Using the tester, measure the resistance between bus bar terminals. Connector & terminal (HV5) P - (HV6) P: (HV5) N - (HV6) N: (HV5) P - (HV9) P: (HV5) N - (HV9) N: (HV7) P - (HV8) P: (HV7) N - (HV8) N:	Is the resistance less than 1 Ω?	Replace the high voltage battery. < Ref. to HIGH VOLTAGE BATTERY .>	Replace the bus bar.

NOTE: Value of «Drive Motor Inverter Input Voltage» is proportional to «Drive Motor Speed».

1000 rpm: 18 V - 37 V
1400 rpm: 25 V - 52 V

Fig 2: Drive Motor Inverter Input Voltage Characteristic Graph
Courtesy of SUBARU OF AMERICA, INC.