Toyota
Nissan Versa
 Sedan Service Manual
Engine » Engine control system (EC) » 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 P0300, P0301, P0302, P0303, P0304. Refer to EC, "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 being stuck open.

DTC No. Trouble diagnosis name (Trouble diagnosis content) DTC detecting condition Possible cause
P0128 THERMSTAT FNCTN [Coolant thermostat (coolant temperature below thermostat regulating temperature)] The engine coolant temperature does not reach to specified temperature even though the engine has run long enough.
  • Thermostat
  • Leakage from sealing portion of thermostat
  • Engine coolant temperature sensor

DTC CONFIRMATION PROCEDURE

NOTE: Never refuel before and during the following procedure.

1.PRECONDITIONINGI

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.

>> GO TO 2.

2.PRECONDITIONINGII

With CONSULT

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

PRECONDITIONINGII

  1. Select "DATA MONITOR" mode of "ENGINE" using CONSULT.
  2. Check the following conditions:

PRECONDITIONINGII

Is the condition satisfied?

YES >> GO TO 3.

NO >> 1. Satisfy the condition. 2. GO TO 3.

3.PERFORM DTC CONFIRMATION PROCEDUREI

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 EMP/S" and "FUEL T/TMP SE" becomes at least 25C (45F).

PERFORM DTC CONFIRMATION PROCEDUREI

*: 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 23C (41F) 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 6C (11F).

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

Is the condition satisfied?

YES >> GO TO 4.

NO >> GO TO 1.

4.PERFORM DTC CONFIRMATION PROCEDUREII

With CONSULT

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

CAUTION: Always drive vehicle at safe speed.

    2.   Check 1st trip DTC.

Is 1st trip DTC detected?

YES >> Proceed to EC, "Diagnosis Procedure".

NO >> INSPECTION END

    More about «P0128 thermostat function»:

    DTC Logic

    Diagnosis Procedure

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