P0128
DTC P0128: Cooling System MalfunctionNOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information.
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 the cooling system. If the cooling system is OK, go to step 20.
NO - Go to step 7.
7. Let the engine cool until the coolant temperature is 104 degrees F (40 degrees 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 ECT SENSOR 1 goes up 49 degrees F (27 degrees C) or more from the recorded temperature.
11. Check ECT SENSOR 2 in the DATA LIST with the HDS.
12. Compare the recorded value of ECT SENSOR 2 and the present value of ECT SENSOR 2.
Did temperature rise 17 degrees F (9.5 degrees C) or more?
YES - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at ECT sensor 1, ECT sensor 2, and the PCM.
NO - Test the thermostat, then go to step 13.
13. Turn the ignition switch ON (II).
14. Reset the PCM with the HDS.
15. Let the engine cool until the coolant temperature is between 21 degrees F (-6 degree C) and 104 degrees F (40 degrees C).
16. Do the PCM idle learn procedure.
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 PCM if it does not have the latest software, or substitute a known-good PCM.
21. Let the engine cool until the coolant temperature is between 21 degrees F (-6 degree C) and 104 degrees F (40 degrees 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 ECT sensor 1, ECT sensor 2, and the 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 PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM.