P0A78-506

Diagnostic trouble codes

DESCRIPTION

Refer to the description of the inverter. (Click here)
If the motor inverter has a circuit malfunction, overheat, or internal short, the inverter transmits this information to the MFIV terminal of the MG ECU via the motor inverter fail signal line.

DTC No.	INF Code	DTC Detection Condition	Trouble Area
P0A78	506	Motor inverter overcurrent signal is detected (overcurrent by HV transaxle assembly malfunction)	Wire harness or connector Hybrid vehicle transaxle assembly w/ converter inverter assembly (MG ECU)

MONITOR DESCRIPTION

If over-amperage flows through the motor inverter due to an internal short, the motor inverter transmits an inverter fail signal to the MG ECU. Upon receiving this signal, the HV control ECU illuminates the MIL and sets a DTC.

INSPECTION PROCEDURE

CAUTION:

Before inspecting the high-voltage system, take safety precautions to prevent electrical shocks, such as wearing insulated gloves and removing the service plug grip. After removing the service plug grip, put it in your pocket to prevent other technicians from reconnecting it while you are working on the high-voltage system.
After disconnecting the service plug grip, wait for at least 5 minutes before touching any of the high-voltage connectors or terminals.

HINT:
: At least 5 minutes is required to discharge the high-voltage capacitor inside the w/ converter inverter assembly.

1. READ OUTPUT DTC (HV)

Connect the intelligent tester to the DLC3.

Turn the ignition switch to the ON position.

Select the following menu items: Powertrain / Hybrid Control / DTC.

Read output DTCs. (Click here)

Result:

The DTCs shown in the table below are output:

DTC No.	Relevant Diagnosis
P0A1D	HV ECU circuit malfunction
P0A2B, P0A2C, P0A2D	Motor temperature sensor circuit
P0A37, P0A38, P0A39	Generator temperature sensor circuit
P0A3F, P0A40, P0A41	Motor resolver circuit
P0A4B, P0A4C, P0A4D	Generator resolver circuit
P0A60, P0A63	Motor current sensor circuit
P0A72, P0A75	Generator current sensor circuit
P0A78 (Except for 506, 806, 807, and 808)	Motor inverter function malfunction
P0A7A	Generator inverter function malfunction
P0A90	Motor function malfunction
P0A92	Generator function malfunction
P0A94 (Except for 554 and 555)	Boost converter circuit
P0AA1, P0AA2, P0AA4, P0AA5	System main relay circuit
P0AA6, P3004	High-voltage system
P3226	Boost converter temperature sensor circuit
P0A79	Rear motor inverter function malfunction
P3216	Rear motor temperature sensor malfunction
P0A45, P0A46, P0A47	Rear motor resolver malfunction
P0A69, P0A6C, P0A55	Rear motor current sensor circuit
P0A1A, P0A1B, P0A1C	MG ECU malfunction

HINT:

Turning the ignition switch to the ON position with the service plug grip and inverter cover removed causes interlock switch system DTC P0A0D-350 to be output.
P0A78-506 may be output due to a malfunction which causes the DTCs in the table above to be output. In this case, first troubleshoot the output DTCs in the table above. Then, perform a reproduction test to check that no DTCs are output.

YES

GO TO DTC CHART

NO

2. CHECK CONNECTION CONDITION OF HYBRID VEHICLE CONTROL ECU CONNECTOR (LOOSENESS AND POOR CONTACT)

Check the connections of the HV control ECU connectors.

OK:

Connectors are connected securely and there is no poor connection.

CONNECT SECURELY

OK

3. CHECK CONNECTION CONDITION OF MG ECU CONNECTOR (LOOSENESS AND POOR CONTACT)

CAUTION:
: Be sure to wear insulated gloves.

Turn the ignition switch off and remove the service plug grip. (Click here)

NOTICE:

Do not put the vehicle into the READY-on state with the service plug grip removed as this may cause a malfunction.

Remove the inverter cover. (Click here)
NOTICE:
1. Wrap the interlock round terminal for the inverter cover with vinyl tape to prevent it from shorting to ground.
2. Prevent water in the reservoir tank from entering the inverter.
3. Removing the inverter cover causes the MG ECU board to be exposed. Therefore, temporarily install the inverter cover for each area to be inspected.

Check the connections of the MG ECU connectors.

OK:

Connectors are connected securely and there is no poor connection.

CONNECT SECURELY

OK

4. CHECK W/ CONVERTER INVERTER ASSEMBLY (MOTOR)

CAUTION:
: Be sure to wear insulated gloves.

Check that the service plug grip is removed.

Check that the bolts for the three-phase AC cable for Motor are tightened to the specified torque.

Torque:: 10 N*m{ 102 kgf*cm , 7 ft.*lbf }

TIGHTEN THEM TO SPECIFIED TORQUE

OK

5. CHECK CONNECTION CONDITION OF MOTOR RESOLVER CONNECTOR

Check the connection of the motor resolver connector.

OK:: Connector is connected securely and there is no poor connection.

CONNECT SECURELY

OK

6. HARNESS AND CONNECTOR (MG ECU - MOTOR RESOLVER)

Disconnect the M7 motor resolver connector.

Measure the voltage according to the value(s) in the table below when the ignition switch is in the ON position.

Standard Voltage:

Tester Connection	Specified Condition
MRF (I24-13) - Body ground	Below 1 V
MRFG (I24-23) - Body ground	Below 1 V
MSN (I24-21) - Body ground	Below 1 V
MSNG (I24-20) - Body ground	Below 1V
MCS (I24-19) - Body ground	Below 1 V
MCSG (I24-18) - Body ground	Below 1 V

Turn the ignition switch off.

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

Standard Resistance (Check for open):

Tester Connection	Specified Condition
MRF (I24-13) - MRF (M7-1)	Below 1 Ω
MRFG (I24-23) - MRFG (M7-4)	Below 1 Ω
MSN (I24-21) - MSN (M7-2)	Below 1 Ω
MSNG (I24-20) - MSNG (M7-5)	Below 1 Ω
MCS (I24-19) - MCS (M7-3)	Below 1 Ω
MCSG (I24-18) - MCSG (M7-6)	Below 1 Ω

Standard Resistance (Check for short):

Tester Connection	Specified Condition
MRF (I24-13) or MRF (M7-1) - Body ground	10 kΩ or higher
MRFG (I24-23) or MRFG (M7-4) - Body ground	10 kΩ or higher
MSN (I24-21) or MSN (M7-2) - Body ground	10 kΩ or higher
MSNG (I24-20) or MSNG (M7-5) - Body ground	10 kΩ or higher
MCS (I24-19) or MCS (M7-3) - Body ground	10 kΩ or higher
MCSG (I24-18) or MCSG (M7-6) - Body ground	10 kΩ or higher

REPLACE HYBRID VEHICLE TRANSAXLE ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR