DTC P0128: Cooling System Malfunction

NOTE:

If the DTCs listed below are stored at the same time as DTC P0128, troubleshoot those DTCs first, then recheck for P0128.
*1: 2004 model

*2: 2004-2006 models

*3: 2005-2006 models

P0106, P0107, P0108, P1128, P1129: MAP sensor

P1106, P1107, P1108 (P2227, P2228, P2229)^*2 :

Barometric pressure circuit

P1259 (P2646)^*1 (P2646, P2647)^*3 : VTEC system

P0401: EGR flow insufficient

P1491 (P0404)^*2 : EGR valve lift insufficient

P1498 (P0406)^*2 : EGR valve lift sensor high voltage

P0116, P0117, P0118 (P0125)^*2 : Engine coolant temperature circuit

P0112, P0113: Intake air temperature sensor

P0500: Vehicle speed sensor

P0335, P0336 (P0339)^*2 : Crankshaft position sensor

P0300: Random misfire

P0301, P0302, P0303: No. 1, No. 2, or No. 3 Cylinder misfire

P0505 (P0506, P0507)^*2 : Idle control system malfunction

P1519 (P0511)^*2 : Idle air control valve
DTC P0128 can set occasionally when the hood is opened while the engine is at normal operating temperature.
Before you troubleshoot, record all freeze data and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).

Check the engine coolant level.
Is the engine coolant level low?
1. YES - Refill the engine coolant. If necessary, check the cooling system.
2. NO - Go to step 2.
Turn the ignition switch ON (II).
Check the radiator fan.
Does the radiator fan keep running?
1. YES - Refer to the radiator fan circuit diagram (see CIRCUIT DIAGRAM ), and troubleshoot the radiator fan circuit; without A/C model (see RADIATOR FAN CIRCUIT TROUBLESHOOTING ), with A/C model (see WITH A/C ) and the radiator fan switch (see RADIATOR FAN SWITCH TEST ).
  Update the ECM if it does not have the latest software, or substitute a known-good ECM; 2000-2001 M/T models (see HOW TO SUBSTITUTE THE ECM FOR TESTING PURPOSES (2000-2001 M/T MODELS) ), 2002-2006 M/T models and CVT model (see ECM UPDATING AND SUBSTITUTION FOR TESTING-2002-2006 M/T MODELS AND CVT MODEL ), then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM (see ECM REPLACEMENT ).
2. NO - Replace the thermostat (see THERMOSTAT REPLACEMENT ).