Code P0128 - Coolant Temperature Below Thermostat Regulating Temperature
problem unless there are some other issues.
The GM TSB dated 2007 recommends reprogramming the PCM as a solution for the code P0128 in 2006 Chevrolet Malibu, Impala, Pontiac G6, and few other models.
The Nissan Technical Service Bulletin (TSB) for the 2007 Nissan Altima and Sentra dated April, 2009 mentions checking the part number of the engine computer with the scan tool and reprogramming it if the part number matches one of the numbers listed in the bulletin.
In some earlier Mazda 3 and Mazda 5 model year vehicles, the code P0128 may be caused by improper calibration of the PCM (engine computer) according to the Mazda service bulletin. The solution is to reprogram the PCM with an updated software and in some Mazda 3s built prior to 2004 also replace the thermostat with an updated part.
For a number of Jeep and Dodge models, we found a couple of Chrysler technical service bulletins that recommend reprogramming the PCM (engine computer) if the code P0128 is diagnosed.
Another Chrysler TSB for 2009-2010 Dodge Challenger and 2008-2010 Dodge Magnum/Charger and Chrysler 300 describes a problem where the thermostat may move out of place allowing coolant to pass through and set the code P0128. The solution is to add a shim and replace the thermostat housing with an updated part.
How the thermostat works
A thermostat is a temperature-operated valve installed in the vehicle cooling system. It controls the coolant flow through the radiator and helps and prevents it from overheating.
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