P0128

DTC P0128: Cooling System Malfunction-'02-03 models

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

P0106, P0107, P0108, P1128, P1129: MAP Sensor
P1106, P1107, P1108: Barometric Pressure Circuit
P1259: VTEC system
P0401: EGR Flow Insufficient
P1491: EGR Valve Lift Insufficient
P1498: EGR Valve Lift Sensor High Voltage
P0116, P0117, P0118: Engine Coolant Temperature Circuit
P0112, P0113: Intake Air Temperature Circuit
P0500: Vehicle Speed Sensor
P0335, P0336: Crankshaft Position Sensor
P0300: Random Misfire
P0301, P0302, P0303: No.1, No.2 or No.3 cylinder misfire
P0505: Idle Control System Malfunction
P1519: Idle Air Control Valve

DTC P0128 can set occasionally when the hood is opened while the engine is at normal operating temperature.

1. Check the engine coolant level.

Is the engine coolant level low?

YES - Refill the engine coolant. If necessary, check the cooling system.

NO - Go to step 2.

2. Turn the ignition switch ON (II).
3. Check the radiator fan.

Does the radiator fan keep running?

YES - Refer to the radiator fan circuit diagram, and troubleshoot the radiator fan circuit and the radiator fan switch.
Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.

NO - Replace the thermostat.