P0128

DTC P0128: Cooling System Malfunction (2005 model)

1. Turn the ignition switch ON (II).
2. Clear the DTC with the HDS.
3. Turn the blower switch OFF.
4. Turn the A/C switch OFF.
5. Check the FAN CTRL in the DATA LIST with the HDS.

Is it OFF?

YES - Go to step 6.

NO - Wait until the FAN CTRL is off, then go to step 6.

6. Check the radiator fan operation.

Does the radiator fan keep running?

YES - Check for symptoms in the cooling system. If they are OK, go to step 20.

NO - Go to step 7.

7. Let the engine cool until the coolant temperature is 104 °F (40 °C) or less.
8. Note the value of ECT SENSOR 1 and ECT SENSOR 2 in the DATA LIST with the HDS.
9. Start the engine, and let it idle.
10. Let the engine idle until the ECT SENSOR goes up 49 °F (27 °C) or more from the recorded temperature.
11. Check the ECT SENSOR 2 in the DATA LIST with the HDS.
12. Compare the value of recorded ECT SENSOR 2 and the value of present ECT SENSOR 2.

Did temperature rise 17 °F (9.5 °C) or more?

YES - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the ECT sensor 1, the ECT sensor 2, and the ECM/PCM.

NO - Test the thermostat, then go to step 13.

13. Turn the ignition switch ON (II).
14. Reset the ECM/PCM with the HDS.
15. Let the engine cool until the coolant temperature is between 21 °F (-6 °C) and 104 °F (40 °C).
16. Do the ECM/PCM idle learn procedure. Programming and Relearning
17. Test-drive at a steady speed between 15 - 75 mph (24 - 120 km/h) for 10 minutes.
18. Check for Temporary DTCs or DTCs with the HDS.

Are any temporary DTCs or DTCs indicated?

YES - If DTC P0128 is indicated, check the cooling system, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.

NO - Go to step 19.

19. Monitor the OBD STATUS for DTC P0128 in the DTCs MENU with the HDS.

Does the screen indicate PASSED?

YES - Troubleshooting is complete.

NO - If the screen indicates FAILED, check the cooling system, then go to step 1. If the screen indicates NOT COMPLETED, go to step 15 and recheck.

20. Update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM.
21. Let the engine cool until the coolant temperature is between 21 °F (-6 °C) and 104 °F (40 °C).
22. Start the engine. Hold the engine speed at 3,000 rpm without load (in Park or neutral) until the radiator fan comes on, then let it idle.
23. Test-drive at a steady speed between 15 - 75 mph (24 - 120 km/h) for 10 minutes.
24. Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?

YES - If DTC P0128 is indicated, check for poor connections or loose terminals at the ECT sensor 1, the ECT sensor 2, and the ECM/PCM, then go to step 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.

NO - If the ECM/PCM was updated, troubleshooting is complete. If the ECM/PCM was substituted, replace the original ECM/PCM.