Dtc Description

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 being stuck open.

DTC DETECTION LOGIC

POSSIBLE CAUSE

• Thermostat

• Leakage from sealing portion of thermostat

• Engine coolant temperature sensor

FAIL-SAFE

Not applicable

Confirmation Procedure

1. CHECK DTC PRIORITY

   If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303 or P0304, first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303 or P0304.

   Is applicable DTC detected?

   YES >>

   Perform diagnosis of applicable. Refer to DTC Index.

   NO >>

   GO TO 2.

2. PRECONDITIONING-1

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

   >>

   GO TO 3.

3. PRECONDITIONING-2

   With CONSULT

   1. Turn ignition switch ON.

   2. Check the following conditions:

      Ambient temperature	−10°C (14°F) or more
      A/C switch	OFF
      Blower fan switch	OFF

   3. Select “DATA MONITOR” mode of “ENGINE” using CONSULT.

   4. Check the following conditions:

      COOLANT TEMP/S

      −10°C – 46°C (14 – 115°F)

   Is the condition satisfied?

   YES >>

   GO TO 4.

   NO >>

   1. Satisfy the condition.

   2. GO TO 4.

4. PERFORM DTC CONFIRMATION PROCEDURE-1

   With CONSULT

   1. Start the engine.

   2. Drive the Nissan Sentra vehicle until the following condition is satisfied.

      CAUTION:

      Always drive vehicle at safe speed.

      1. STEP 1

         Drive the Nissan Sentra vehicle under the conditions instructed below until the difference between “COOLANT TEMP/S” and “FUEL T/TMP SE” becomes at least 21°C (38°F).

         COOLANT TEMP/S	65°C (149°F) or less
         FUEL T/TMP SE	Less than the value calculated by subtracting 21°C (38°F) from “COOLANT TEMP/S”.*

         *: Example

         COOLANT TEMP/S	FUEL T/TMP SE
         70°C (158°F)	49°C (120°F) or less
         65°C (149°F)	44°C (111°F) or less
         60°C (140°F)	39°C (102°F) or less

      2. STEP 2

         Drive the Nissan Sentra vehicle at 50 km/h (32 MPH) or more with the difference between “COOLANT TEMP/S” and “FUEL T/TMP SE” maintained at 21°C (38°F) or more.

         Note:

         Keep the accelerator pedal as steady as possible during cruising.

      3. STEP 3

         Drive the Nissan Sentra vehicle at 50 km/h (32 MPH) or more until “COOLANT TEMP/S” increases by 6°C (11°F).

         Note:

         Keep the accelerator pedal as steady as possible during cruising.

   Is the condition satisfied?

   YES >>

   GO TO 5.

   NO >>

   GO TO 2.

5. PERFORM DTC CONFIRMATION PROCEDURE-2

   With CONSULT

   1. Drive the Nissan Sentra vehicle until the following condition is satisfied.

      COOLANT TEMP/S

      59°C (139°F) or more

      CAUTION:

      Always drive Nissan Sentra vehicle at safe speed.

   2. Check 1st trip DTC.

   Is 1st trip DTC detected?

   YES >>

   Proceed to DTC Description.

   NO-1 >>

   To check malfunction symptom before repair: Refer to Intermittent Incident.

   NO-2 >>

   Confirmation after repair: INSPECTION END

Dtc Diagnosis Procedure

1. CHECK ENGINE COOLANT TEMPERATURE SENSOR

   Refer to Component Inspection.

   Is the inspection result normal?

   YES >>

   GO TO 2.

   NO >>

   Replace engine coolant temperature sensor. Refer to Exploded View.

2. CHECK THERMOSTAT

   Check the thermostat. Refer to Inspection.

   Is the inspection result normal?

   YES >>

   INSPECTION END

   NO >>

   Replace thermostat. Refer to Removal and Installation.