Diagnosis Procedure

WARNING: This page is about a different car, the 2020 Infiniti QX60. However, it is still accessible from the selected car via links, so may be relevant.

CHECK DTC PRIORITY
If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306, first perform the confirmation procedure (trouble diagnosis) for DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306.

Is DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306 detected?

YES

Perform diagnosis of applicable. Refer to DTC Description .

NO

GO TO 2.
CHECK ENGINE COOLANT TEMPERATURE SENSOR
Check engine coolant temperature sensor. Refer to Component Inspection (Engine Coolant Temperature Sensor) .

Is the inspection result normal?

YES

GO TO 3.

NO

Replace engine coolant temperature sensor.
CHECK THERMOSTAT
Check thermostat. Refer to Removal and Installation .

Is the inspection result normal?

YES

INSPECTION END

NO

Replace thermostat assembly. Refer to Removal and Installation .

CHECK DTC PRIORITY
If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306, first perform the confirmation procedure (trouble diagnosis) for DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306.

Is DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306 detected?

YES

Perform diagnosis of applicable. Refer to DTC Description .

NO

GO TO 2.
CHECK ENGINE COOLANT TEMPERATURE SENSOR
Check engine coolant temperature sensor. Refer to Component Inspection (Engine Coolant Temperature Sensor) .

Is the inspection result normal?

YES

GO TO 3.

NO

Replace engine coolant temperature sensor.
CHECK THERMOSTAT
Check thermostat. Refer to Removal and Installation .

Is the inspection result normal?

YES

INSPECTION END

NO

Replace thermostat assembly. Refer to Removal and Installation .