Nissan Altima HL32 Hybrid. Manual - part 620

P0A78-121

HBC-229

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P0A78-121

Description

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The inverter converts high-voltage direct current from the HV battery and alternating current for MG2 and

MG1. The inverter contains a three-phase bridge circuit, which consists of six power transistors each for MG2

and MG1, that converts direct current to three-phase alternating current. The MG ECU controls the actuation

of the power transistors. The inverter transmits information that is necessary for effecting control, such as the

amperage and voltage, to the MG ECU.

The MG ECU uses a voltage sensor, which is built into the inverter, to detect boosted high voltage to allow

control of the voltage boost.

The inverter voltage sensor outputs voltage that varies between 0 and 5 V in accordance with the changes in

the high voltage. The higher the high voltage, the higher the output voltage, and the lower the high voltage, the

lower the output voltage.

HBC-230

< COMPONENT DIAGNOSIS >

P0A78-121

The MG ECU monitors the inverter voltage and detects malfunctions.

DTC Logic

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DTC DETECTION LOGIC

JMCIA0099GB

DTC No.

INF Code

Trouble diagnosis name

DTC detecting condition

Possible cause

P0A78

121

Drive Motor “A” Inverter 
Performance

Motor inverter overvoltage signal detection 
(overvoltage due to system malfunction)

• HV relay assembly
• Inverter with converter assembly
• Service plug grip
• Frame wire
• Hybrid transaxle

P0A78-121

HBC-231

< COMPONENT DIAGNOSIS >

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Diagnosis Procedure

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1.

PRECONDITIONING

• Before inspecting the high-voltage system or disconnecting the low voltage connector of the inverter with

converter assembly, take safety precautions such as wearing insulated gloves and removing the service

plug grip to prevent electrical shocks. After removing the service plug grip, put it in your pocket to prevent

other technicians from accidentally reconnecting it while you are working on the high-voltage system.

• After disconnecting the service plug grip, wait for at least 10 minutes before touching any of the high-voltage

connectors or terminals.

• Waiting for at least 10 minutes is required to discharge the high-voltage capacitor inside the inverter with

converter assembly.

>> GO TO 2.

2.

CHECK DTC OUTPUT (HYBRID SYSTEM)

1. Turn ignition switch ON.

2. Check DTC.

NOTE:

P0A78-121 may be set due to a malfunction which also causes DTCs in the table above to be set. In this

case, first troubleshoot the output DTCs in the table above.

Then, perform a test to attempt to reproduce the problems, and check that no DTCs are output.

Is DTC detected?

OK

>> Go to Diagnosis Procedure relevant to output DTC.

DTC No.

Relevant Diagnosis

P0A1D (Except INF code 390)

Hybrid Powertrain Control Module

P0A1A (all INF codes)

Generator Control Module

P0A1B (all INF codes)

Drive Motor “A” Control Module

P0A72 (all INF codes)

Generator Phase V Current

P0A75 (all INF codes)

Generator Phase W Current

P0A60 (all INF codes)

Drive Motor “A” Phase V Current

P0A63 (all INF codes)

Drive Motor “A” Phase W Current

P0A51-174

Drive Motor “A” Current Sensor Circuit

P0A4B-253

Generator Position Sensor Circuit

P0A4D-255

Generator Position Sensor Circuit Low

P0A4C-513

Generator Position Sensor Circuit Range / Performance

P0A3F-243

Drive Motor “A” Position Sensor Circuit

P0A40-500

Drive Motor “A” Position Sensor Circuit Range / Performance

P0A41-245

Drive Motor “A” Position Sensor Circuit Low

P0A78-266, 267, 523, 586, 284, 505, 287, 506, 
113, 286, 503, 279, 504, 306, 806, 807, 808, 128

Drive Motor “A” Inverter Performance

P0A94-585, 587, 589, 590, 553, 554, 555, 556, 
172, 557, 547, 548, 549, 442

DC/DC Converter Performance

P0A7A-322, 517, 325, 518, 122, 324, 344, 809, 
810, 811, 130

Generator Inverter Performance

P0A92-521

Hybrid Generator Performance

P0A90-509

Drive Motor “A” Performance

P3004-803

High Voltage Power Resource

P0ADB-227

Hybrid Battery Positive Contactor Control Circuit Low

P0ADC-226

Hybrid Battery Positive Contactor Control Circuit High

P0ADF-229

Hybrid Battery Negative Contactor Control Circuit Low

HBC-232

< COMPONENT DIAGNOSIS >

P0A78-121

NG

>> GO TO 3.

3.

CHECK CONNECTOR CONNECTION CONDITION (INVERTER WITH CONVERTER ASSEMBLY CON-

NECTOR)
See 

HBC-109, "Diagnosis Procedure"

.

OK or NG

OK

>> GO TO 4.

NG

>> Connect securely.

4.

CHECK HARNESS AND CONNECTOR (INVERTER WITH CONVERTER ASSEMBLY - GENERATOR RE-

SOLVER)
See 

HBC-164, "Diagnosis Procedure"

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OK or NG

OK

>> GO TO 5.

NG

>> Repair or replace harness or connector.

5.

CHECK GENERATOR RESOLVER

See 

HBC-164, "Diagnosis Procedure"

.

OK or NG

OK

>> GO TO 6.

NG

>> GO TO 21.

6.

CHECK HARNESS AND CONNECTOR (INVERTER WITH CONVERTER ASSEMBLY - MOTOR RESOLV-

ER)
See 

HBC-171, "Diagnosis Procedure"

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OK or NG

OK

>> GO TO 7.

NG

>> Repair or replace harness or connector.

7.

CHECK MOTOR RESOLVER

See 

HBC-171, "Diagnosis Procedure"

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OK or NG

OK

>> GO TO 8.

NG

>> GO TO 19.

8.

CHECK INVERTER WITH CONVERTER ASSEMBLY (MOTOR CABLE CONNECTION CONDITION)

See 

HBC-177, "Diagnosis Procedure"

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OK or NG

OK

>> GO TO 9.

NG

>> Tighten to specified torque.

9.

CHECK INVERTER WITH CONVERTER ASSEMBLY (GENERATOR CABLE CONNECTION CONDITION)

See 

HBC-177, "Diagnosis Procedure"

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OK or NG

OK

>> GO TO 10.

NG

>> Tighten to specified torque.

10.

INSPECT HYBRID TRANSAXLE (MG1)

See 

HBC-177, "Diagnosis Procedure"

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OK or NG

OK

>> GO TO 11.

NG

>> Replace hybrid transaxle (See page HX-10)

11.

INSPECT HYBRID TRANSAXLE (MG2)

See 

HBC-177, "Diagnosis Procedure"

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OK or NG