Nissan Maxima Service and Repair Manual: P0128 thermostat function

DTC Logic

DTC DETECTION LOGIC

NOTE: If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306, first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306.

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

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

DTC CONFIRMATION PROCEDURE

NOTE: Never refuel before and during the following procedure.

1.PRECONDITIONING-I

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.

1. Turn ignition switch OFF and wait at least 10 seconds.
2. Turn ignition switch ON.
3. Turn ignition switch OFF and wait at least 10 seconds.

2.PRECONDITIONING-II

With CONSULT

1. Turn ignition switch ON.
2. Check the following conditions:

3. Select "DATA MONITOR" mode of "ENGINE" using CONSULT.
4. Check the following conditions:

3.PERFORM DTC CONFIRMATION PROCEDURE-I

With CONSULT

1. Start engine.
2. Drive the vehicle until the following condition is satisfied

CAUTION: Always drive vehicle at safe speed.

•  STEP 1

Drive the vehicle under the conditions instructed below until the difference between "COOLAN TEMP/S" and "FUEL T/TMP SE" becomes at least 25C (45F).

*: Example

• STEP 2 Drive the vehicle at 50 km/h (32 MPH) or more with the difference between "COOLAN TEMP/S" and "FUEL T/TMP SE" maintained at 25C (45F) or more.

  NOTE: Keep the accelerator pedal as steady as possible during cruising.

•  STEP 3 Drive the vehicle at 50 km/h (32 MPH) or more until "COOLAN TEMP/S" increases by 7C (13F).

  NOTE: Keep the accelerator pedal as steady as possible during cruising.

4.PERFORM DTC CONFIRMATION PROCEDURE-II

With CONSULT

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

CAUTION: Always drive vehicle at safe speed.

2. Check 1st trip DTC.

Diagnosis Procedure

1.CHECK ENGINE COOLANT TEMPERATURE SENSOR

2.CHECK THERMOSTAT

Check 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. Refer to CO-24, "Removal and Installation".
4. Check resistance between engine coolant temperature sensor terminals as per the following.