# bad thermostat, P0128



## mblaundry (Dec 30, 2018)

Hello everyone!
I have 2004 Altima 2.5 that just popped P0128 code for bad thermostat .
I watched a few videos already and some Altimas have 2 thermostat , one on lower hose connector and one on the upper right of the engine.
How can I find out if I have both or only one?


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## rogoman (Dec 16, 2004)

The 2002 - 2012 2.5 altimas had two thermostats. The main one feeds the radiator. The second one is called a water control valve which feeds several accessories such as the heater and oil cooler; it's purpose is quicker warmup for the accessories. If it's stuck closed, it could possibly cause overheating.


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## mblaundry (Dec 30, 2018)

Rogoman, do you happened to know witch one would fail on code P0128?


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## rogoman (Dec 16, 2004)

The P0128 code only tells you that the engine coolant temperature has not reached the specified temperature even though the engine has run long enough. You would have to test or replace one or both thermostats. Also the temp sensor may be bad.

Possible causes:
● Bad thermostat(s)
● Leakage from sealing portion of thermostat
● Bad engine coolant temperature sensor


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