Nissan Altima (L32) 2007-2012 Service Manual: P0128 Thermostat function

DTC Logic

DTC DETECTION LOGIC

NOTE: If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303 or P0304, first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304. Refer to EC-776, "DTC Logic".

Engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough.

This is due to a leak in the seal or the thermostat stuck open.

DTC CONFIRMATION PROCEDURE

1.PRECONDITIONING

If DTC CONFIRMATION PROCEDURE has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test.

TESTING CONDITION: • For best results, perform at ambient temperature of –10°C (14°F) or higher.

• Before performing the following procedure, do not fill with the fuel.

>> GO TO 2.

2.PERFORM DTC CONFIRMATION PROCEDURE

1. Turn A/C switch OFF.

2. Turn blower fan switch OFF.

3. Turn ignition switch ON.

4. Select “COOLAN TEMP/S” in “DATA MONITOR” mode with CONSULT-III.

5. Check the indication of “COOLAN TEMP/S” If it is below 52°C (126°F), go to following step.

If it is above 52°C (126°F), cool down the engine to less than 52°C (126°F). Then go to next steps.

6. Start engine.

7. Drive vehicle for 10 consecutive minutes under the following conditions.

CAUTION: Always drive vehicle at a safe speed.

If “COOLAN TEMP/S” increases to more than 71°C (160°F) within 10 minutes, turn ignition switch OFF because the test result will be OK.

8. Check 1st trip DTC.

Follow the procedure “With CONSULT-III” above.

Is 1st trip DTC detected? YES >> Go to EC-722, "Diagnosis Procedure".

NO >> INSPECTION END

Diagnosis Procedure

1.CHECK ENGINE COOLANT TEMPERATURE SENSOR

Refer to EC-723, "Component Inspection".

Is the inspection result normal? YES >> GO TO 2.

NO >> Replace engine coolant temperature sensor.

2.CHECK THERMOSTAT

Refer to CO-21, "Removal and Installation".

Is the inspection result normal? YES >> INSPECTION END NO >> Replace thermostat.

Component Inspection

1.CHECK ENGINE COOLANT TEMPERATURE SENSOR

1. Turn ignition switch OFF.

2. Disconnect engine coolant temperature sensor harness connector.

3. Remove engine coolant temperature sensor.

4. Check resistance between engine coolant temperature sensor terminals by heating with hot water as shown in the figure.

Is the inspection result normal? YES >> INSPECTION END

NO >> Replace engine coolant temperature sensor.