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

P0401: Exhaust Gas Recirculation (EGR) System Flow

P0116, P0117, P0118: Engine Coolant Temperature (ECT) sensor

P0112, P0113: Intake Air Temperature (IAT) sensor

P0335, P0336: Crankshaft Position (CKP) sensor

P0300: Random misfire

P0301, P0302, P0303, P0304, P0305, P0306: No. 1, No. 2, No. 3, No. 4, No. 5 or No. 6 cylinder misfire

P0505: Idle control system

P1519: Idle Air Control (IAC) valve

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

Turn the ignition switch ON (II).
Check the radiator fan.
Does the radiator fan keep running?
1. YES -Check the radiator fan circuit (see ELECTRIC COOLING FANS ), the radiator fan switch circuit (see ELECTRIC COOLING FANS ), and the radiator fan switch (see ELECTRIC COOLING FANS ). If they are OK, substitute a known-good PCM and recheck (see HOW TO SUBSTITUTE THE PCM FOR TESTING ). If the symptom/indication goes away, replace the original PCM.
2. NO -Go to step 3.
Reset the PCM (see HOW TO RESET THE PCM ).
Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
Is DTC P0128 indicated?
1. YES -Test the thermostat (see THERMOSTAT TEST ).
2. NO -Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the radiator fan sensor and the PCM.