Lexus NX manuals

Lexus NX: Motor Electronics Coolant Temperature Sensor Circuit Range / Performance (P0A01-726,P0A04-725)

Lexus NX Service Manual / Engine & Hybrid System / 2ar-fxe (hybrid / Battery Control) / Hybrid Control System / Motor Electronics Coolant Temperature Sensor Circuit Range / Performance (P0A01-726,P0A04-725)

DTC SUMMARY

MALFUNCTION DESCRIPTION

These DTCs indicate the temperature sensor value is abnormal. The cause of this malfunction may be one of the following:

Area

Main Malfunction Description

Step
Inverter low-voltage circuit

The connectors are not connected properly

2

Hybrid cooling system

Coolant circulation abnormal (frozen or leaking, etc.)

3
Inside of inverter

Inverter with converter assembly internal circuit malfunction

3

DESCRIPTION

The hybrid vehicle control ECU detects HV coolant temperature using the coolant temperature sensor built into the inverter with converter assembly. The hybrid vehicle control ECU uses signals from the coolant temperature sensor to check the effectiveness of the inverter cooling system. If necessary, the hybrid vehicle control ECU will limit inverter output to help prevent inverter overheating. The hybrid vehicle control ECU also detects malfunctions in the sensor based on the HV coolant temperature sensor values. The inverter with converter assembly detects malfunctions in the HV coolant temperature sensor and its wiring.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

MIL

Warning Indicate

P0A01-726

Motor Electronics Coolant Temperature Sensor Circuit Range / Performance

Abnormal deviation in inverter coolant temperature sensor output.

Both of the following conditions are met for 10 seconds or more:

  • The difference between the estimated coolant (for inverter) temperature and the temperature sensor output is large.
  • Coolant (for inverter) temperature is too high.

(1 trip detection logic)
  • Inverter cooling system
  • Cooling fan system
  • Inverter with converter assembly
  • Wire harness or connector

Comes on

Master Warning Light:

Comes on

P0A04-725

Motor Electronics Coolant Temperature Sensor Circuit Intermittent

Sudden change in HV coolant temperature sensor output or hunting:

Unusual sudden change in HV coolant temperature sensor output occurs and the offset continues for a certain period of time.

Unusual sudden change in HV coolant temperature sensor output occurs repeatedly.

(1 trip detection logic)
  • Inverter cooling system
  • Cooling fan system
  • Inverter with converter assembly
  • Wire harness or connector

Comes on

Master Warning Light:

Comes on
Related Data List

DTC No.

ECU Data List

P0A01-726
  • Inverter Coolant Water Temperature
  • Ambient Temperature
  • (Inverter) W/P Run Control Duty
  • Inverter W/P Revolution

P0A04-725

MONITOR DESCRIPTION

If the hybrid vehicle control ECU detects a malfunction of the HV coolant temperature sensor, it will illuminate the MIL and store a DTC.

MONITOR STRATEGY

Related DTCs

P0A01 (INF 726): Motor Electronics Coolant Temperature Sensor Circuit Range / Performance

P0A04 (INF 725): Motor Electronics Coolant Temperature Sensor Circuit Intermittent

Required sensors/components

HV coolant temperature sensor

Frequency of operation

Continuous

Duration

TMC's intellectual property

MIL operation

1 driving cycle

Sequence of operation

None

TYPICAL ENABLING CONDITIONS

The monitor will run whenever the following DTCs are not stored

TMC's intellectual property

Other conditions belong to TMC's intellectual property

-

TYPICAL MALFUNCTION THRESHOLDS

TMC's intellectual property

-

COMPONENT OPERATING RANGE

Hybrid vehicle control ECU

DTC P0A01 (INF 726) is not detected

DTC P0A04 (INF 725) is not detected

CONFIRMATION DRIVING PATTERN

  1. Connect the Techstream to the DLC3.
  2. Turn the power switch on (IG) and turn the Techstream on.
  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).
  4. Turn the power switch off and wait for 30 seconds or more.
  5. Turn the power switch on (IG) and turn the Techstream on.
  6. Turn the power switch on (READY).
  7. With the shift lever in P, wait for 90 seconds. [A]

    HINT:

    Check that there are no abnormalities (abnormal sounds, coolant leaks, DTC output, etc).

  8. Perform a road test according to the freeze frame data "Vehicle Spd" for approximately 10 minutes. [B]
  9. Enter the following menus: Powertrain / Hybrid Control / Trouble Codes. [C]
  10. Read the current DTCs.

    HINT:

    • If a current DTC is output, the system is malfunctioning.
    • If a current DTC is not output and want to confirm permanent DTC, perform the following procedure.
  11. Check that permanent DTCs are cleared. If no permanent DTC is output, the system is normal.
  12. If the permanent DTCs are not cleared, perform a universal trip, and then check for permanent DTCs again.

CAUTION / NOTICE / HINT

CAUTION:

  • 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 removing the service plug grip, wait for at least 10 minutes before touching any of the high-voltage connectors or terminals. After waiting for 10 minutes, check the voltage at the terminals in the inspection point in the inverter with converter assembly. The voltage should be 0 V before beginning work.

    Click here

    HINT:

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

NOTICE:

After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.

Click here

HINT:

After the repair, clear the DTCs and perform the following procedure to check that DTCs are not output.

  1. Turn the power switch on (READY) and wait for 90 seconds or more.
  2. Drive the vehicle for approximately 10 minutes referring to the following freeze frame data or Data List items: "Vehicle Spd".

PROCEDURE

1.

CHECK DTC OUTPUT (HYBRID CONTROL)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Enter the following menus: Powertrain / Hybrid Control / Trouble Codes.

(d) Check for DTCs.

Powertrain > Hybrid Control > Trouble Codes

Result

Proceed to

P0A01-726 or P0A04-725 only is output, or DTCs except the ones in the table below are also output.

A

Any of the following DTCs are also output.

B

Relevant DTC

P0A93-346

Inverter Cooling System Performance

P0C73-776

Motor Electronics Coolant Pump "A" Control Performance

P314A-828

Inverter Coolant Pump Speed Signal

HINT:

P0A01-726 or P0A04-725 may be output as a result of the malfunction indicated by the DTCs above.

(e) Turn the power switch off.

B

GO TO DTC CHART (HYBRID CONTROL SYSTEM)

A

2.

CHECK CONNECTOR CONNECTION CONDITION (INVERTER WITH CONVERTER ASSEMBLY CONNECTOR)

Click here

Result

Proceed to

OK

A

NG (The connector is not connected securely.)

B

NG (The terminals are not making secure contact or are deformed, or water or foreign matter exists in the connector.)

C
B

CONNECT SECURELY
C

REPAIR OR REPLACE HARNESS OR CONNECTOR
A

3.

CHECK COOLING SYSTEM

Click here

HINT:

If the "Cooling System" inspection results are normal, perform the next step.

NEXT

REPLACE INVERTER WITH CONVERTER ASSEMBLY

READ NEXT:

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