Advanced Diagnostics

Advanced Diagnostics - DTC P0A78 (32): Motor Control Module (MCM) Internal Circuit Malfunction






General Description
There is a motor control processor and a motor control subprocessor in the motor control module (MCM), and the following malfunctions are detected with the motor control processor.

Symptom 1
From the motor control subprocessor, the motor control processor receives power supply circuit voltage (H+8V), and constant current circuit detection voltage which is the value of the current changed to voltage used for internal temperature compensation. It also receives a constant current circuit reference voltage and a platinum sensor disconnection threshold value which is the compensation resistance value from the motor control subprocessor. When the information is not sent from the motor control subprocessor and this condition continues for a specified time, or when the information sent from the motor control subprocessor contains abnormal information and this condition continues for a specified time, the motor control processor detects a malfunction and a DTC is stored.

Symptom 2
When a power supply circuit voltage (H+8V), a constant current circuit detection voltage, a constant current circuit reference voltage, or a platinum sensor disconnection threshold value received from the motor control sub processor exceeds an upper or lower value, or changes for a specified time, the motor control processor detects a malfunction and a DTC is stored. However, a malfunction is not judged when only the platinum sensor disconnection threshold value changes.

Symptom 3
The motor control processor reads the power supply circuit voltage (L+8V), the over current upper threshold voltage which is the reference voltage of the circuit that detects high side over current, and the over current lower threshold voltage which is the reference voltage of the circuit that detects low side over current. When either the low voltage power supply circuit voltage (L+8V), the over current upper threshold voltage, or the over current lower threshold voltage exceeds the upper limit setting, the lower limit setting, or fluctuates for a specified time, the motor control processor detects a malfunction and a DTC is stored.

Symptom 4
The monitor control processor and the CAN controller for the IMA-CAN communication communicate serially. When the signal to the CAN controller and the return signal differ for a set number of cycles, a malfunction is detected and a DTC is stored.

Symptom 5
The monitor control processor receives over voltage (0 V) from the motor control subprocessor via PORT. (The motor control subprocessor detects that primary voltage of the motor is too high and this information is sent to the PORT of the motor control processor.) When the motor control subprocessor outputs abnormal condition information to the PORT more than once even though the control voltage of the motor control processor is within the normal range, the over voltage signal line detects a malfunction and a DTC is stored.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold

Symptom 1
Information is not sent from the motor control sub processor for at least 500 milliseconds, or information sent from the motor control subprocessor includes abnormal condition information for at least 0.5 second.

Symptom 2 (One of the following conditions occurs)
- The power supply circuit voltage (L+8V) is 4.30 V or more, or 2.47 V or less, for at least 40 milliseconds, or its deviation is 1.07 V or more for at least 40 milliseconds.
- The constant current circuit detection voltage is 0.91 V or more, or 0.53 V or less, for at least 40 milliseconds, or its deviation is 1.07 V or more for at least 40 milliseconds.
- The constant current circuit reference voltage is 0.84 V or more, or 0.6 V or less, for at least 40 milliseconds, or its deviation is 1.07 V or more for at least 40 milliseconds.
- The platinum sensor disconnection threshold value is 4.66 V or more, or 1.8 V or less, for at least 0.8 second.

Symptom 3 (One of the following conditions occurs)
- The power supply circuit voltage (L+8V) is 3.78 V or more, or 2.2 V or less, for at least 40 milliseconds, or its deviation is 1.07 V or more for at least 40 milliseconds.
- The over current upper limit threshold voltage is 5.0 V or more, or 3.47 V or less, for at least 40 milliseconds, or its deviation is 1.07 V or more for at least 40 milliseconds.
- The over current lower limit threshold voltage is 0.87 V or more, or 0.2 V or less, for at least 40 milliseconds, or its deviation is 1.07 V or more for at least 40 milliseconds.

Symptom 4
The signal to the CAN controller and the return signal differ at least three times.

Symptom 5
The over voltage notification is input three times in 25 seconds even though the control voltage is 235 V or less.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected, the MIL comes on and a Pending DTC, a Confirmed DTC, and the freeze data are stored in the PCM and the MCM memory.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.