P0128 Thermostat OBD-II Trouble Code

Description and meaning of DTC p0128

This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to OBD-II equipped vehicles. Brands of vehicles that may see this code include but are not limited to Pontiac, Toyota, Mazda, Dodge, Chevrolet, Honda, Jeep, Ford, VW, etc. Although generic, the specific repair steps may vary depending on make/model. This means that the engine's powertrain control module (PCM) has detected that the engine has not reached therequired temperature level within a specified amount of time after startingthe engine. Often, the intent of the P0128 code is to indicate a faulty thermostat (likely stuck in the open condition). Similar codes: P0125In determining that the engine did not reach a "normal" temperature, ittakes into account the length of time the vehicle has been running, the intakeair temperature (IAT) sensor reading, the engine coolant temperature (ECT) sensorreading, and the speed of the vehicle.

p0128 diagnostic trouble code symptoms

You will likely not notice any drivability problems other than the MILillumination. In some cases you may experience symptoms such as:Engine takes longer to warm upEngine temperature drops while driving at higher speeds

DTC p0128 - possible causes

A code P0128 may mean that one or more of the following has happened:Low engine coolant level Leaking or stuck open thermostat (likely)Faulty cooling fan (running too much) Faulty coolant temperature (ECT) sensorFaulty intake air temperature (IAT) sensor

How to fix OBD-II diagnostic trouble code p0128

Note: Please be sure the engine is turned off and cool when doing work on the cooling system. When the engine is warm, the cooling system is pressurized and very hot and can cause burns or other personal injuries if you are not careful. Past experience indicates that the most likely solution for a P0128 is to replace the thermostat. However here are some suggestions on troubleshooting and repairing a P0128 OBD-IIcode:Verify coolant strength levelVerify proper cooling fan operation (check if it's running more than itshould). Replace if necessary. Verify proper engine coolant temperature (ECT) sensor operation, replaceif necessary. Verify proper intake air temperature (IAT) sensor operation, replace ifnecessary. If the above items check out good, replace the thermostatIf Nissan vehicle, check for Technical Service Bulletins (TSBs), as the ECM may need to be reprogrammed to correct the P0128 codeRegardless of what vehicle year, make and model, it is advisable to check for TSBs because if there is a known fix set out by the automaker, it can save you time and money in the diagnosis and repair. Other ECT sensor and circuit related DTCs: P0115, P0116, P0117, P0118, P0119, P0125

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