DTC DETECTION LOGIC NOTE： If DTC P0128 is displayed with DTC P0300, P0301, P0302, P0303 or P304, first perform the trouble diagnosis for DTC P0300, P0301, P0302, P0303, P0304. Refer to DTC Logic (GT-R certified NISSAN dealer). 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 No. | Trouble diagnosis name | DTC detecting condition | Possible cause
P0128 | Thermostat function | 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
1.PRECONDITIONING
If DTC Confirmation Procedure has been previously conducted, always perform the following 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.

TESTING CONDITION:

- For best results, perform at ambient temperature of –10°C (14°F) or higher.
- For best results, perform at engine coolant temperature of –10°C (14°F) to 51°C (124°F).
- 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 51°C (124°F), go to the following step.If it is above 51°C (124°F), cool engine down to less than 51°C (124°F). Then go to next step.
6. Start engine.
7. Drive vehicle for 10 consecutive minutes under the following conditions.

   VHCL SPEED SE | More than 56 km/h (35 MPH)

   ■ CAUTION ■
   Always drive vehicle at a safe speed
   NOTE：
   If “COOLAN TEMP/S” increases to more than 70°C (158°F) with in 10 minutes, turn ignition switch OFF because the test result will be OK.
8. Check 1st trip DTC.

Is 1st trip DTC detected?
YES>>Go to Diagnosis Procedure (GT-R certified NISSAN dealer).
NO>>INSPECTION END