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,P1107, P1108 (P2227, P2228, P2229)*: Barometric Pressure (BARO) sensor
P1259 (P2246, P2247)*: VTEC system
P0116, P0117, P0118 (P0125)*: Engine Coolant Temperature (ECT) sensor
P0112, P0113: Intake Air Temperature (IAT) sensor
P0500: Vehicle Speed Sensor (VSS)
P0335, P0336 (P0339)*: Crankshaft Position (CKP) sensor
P0300: Random misfire detected
P0301, P0302, P0303, P0304: No.1, No.2, No.3 or No.4 cylinder misfire detected
P0505 (P0506, P0507)*: Idle control system malfunction
P1519 (P0511)*: Idle Air Control (IAC) valve
*:04 model

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), and make sure the A/C is off.
3. Check the radiator fan.

Does the radiator fan run continuously?

YES - Check the radiator fan circuit, the radiator fan switch circuit open, the radiator fan switch circuit short, 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.