P0128

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.

P0107, P0108, P1128, P1129: Manifold Absolute Pressure (MAP) sensor
P1106, 1107, P1108: Barometric Pressure (BARO) sensor
P1259: VTEC system
P0116, P0117, P0118: Engine Coolant Temperature (ECT) sensor
P0112, P0113: Intake Air Temperature (IAT) sensor
P0500, P0501: Vehicle Speed Sensor (VSS)
P0335, P0336: Crankshaft Position (CKP) sensor
P0300: Random misfire
P0301, P0302, P0303, P0304: No.1, No.2, No.3 or No.4 cylinder misfire
P0505: Idle control system Malfunction
P1519: Idle Air Control (IAC) valve

DTC P0128 can occasionally set when the hood is opened while the engine is running.

1. Check the engine coolant level.

Is the engine coolant level low?

YES - Refill the engine coolant. If necessary, repair the coolant leak.

NO - Go to step 2.

2. Turn the ignition switch ON (II).
3. Check the radiator fan. (Make sure the A/C is off.)

Does the radiator fan run continuously?

YES - Check the radiator fan circuit, the radiator fan switch circuit, and the radiator fan switch. If they are OK, update the ECM/PCM if it does not have the latest software, or substitute a known-good ECM/PCM, then recheck. If the symptom/indication goes away with a known-good ECM/PCM, replace the original ECM/PCM.

NO - Replace the thermostat.