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: Barometric pressure (BARO) sensor
P1259: VTEC system
P0116, P0117, P0118: Engine coolant temperature (ECT) sensor
P0112, P0113: Intake air temperature (IAT) sensor
P0500: 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 leakage.

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 keep running?

YES - Check the radiator fan circuit, the radiator fan switch circuit (Short), and the radiator fan switch. Also, inspect the ECT and IAT circuits and terminal connections. If the circuits, the switch, and the connections are OK, 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.