Chevy Cavalier P0128

Question:
My check engine light came on about 1 week ago. I brought it to AutoZone and they gave me a Code P0128. Probable causes: Check Coolant Level - checked and ok Thermostat Defective - put a new one in today ECT Sensor Defective - No replacement part available at AutoZone. Check Engine Light codes P0128. Repair done prior = A year ago hired a mechanic to supposedly change thermostat due to overheating engine. Done to repair = Went to Autozone and got the code P0128. Sales associate suggested i change the thermostat so i purchased one and "replaced" it today. Also just found out today that the mechanic hired last year to replace old thermostat never put in a new one. No wonder during the winter months i had no heat..

After placing the new thermostat in place and filling the reservoir with fresh antifreeze (50/50 Dexcool), I turned on the ignition and then noticed the engine temperature gauge raised up too fast just past the halfway point in a matter of minutes. Check engine light still on.

Related:

Answer:
It is possible the sensor is bad, or you have air in the cooling system. This code normally comes on because the engine coolant temp has not reached normal operating temp within a per-determined time. Air pockets around the sensor will cause it to not read properly. I suggest replacing the temperature sensor and bleeding the cooling system of air pockets.

Question:
2001 Chevy Impala coolant radiator fan keeps running even after the engine is turned off. It runs for about 15 minutes or so. The temperature gauge quit working at the same time this problem started. Any suggestions? Thanks.

Answer:
if you are referring to the radiator fan, it sounds like you are describing a pretty common problem. I'll bet the check engine light is on also. If it is then you probably have a trouble codes stored – P0128. This code is described as "coolant temperature below thermostat threshold". Basically the thermostat is stuck open and the engine is not getting up to proper operating temperature. That's why the gauge looks like it quit working but it actually is, just showing cold coolant temperature.

The fan staying on is the computer going into sort of a safe mode. Since it does not know what temperature the coolant is, it turns the fan on in case it's too hot, to prevent the engine from overheating. Get the thermostat replaced, the code cleared, and you will be good to go. This is assuming that your antifreeze is not low. If it were low you have the same problems as above because the sensor cannot read air, it must be touching coolant. So check that first.

I was at my wits end because of my 2.2 Cavalier overheating.I tried everything short of a water pump and head gasket but then read on a forum to move the thermostat back to the upper part of engine like on the older cavaliers. I put a gasket in the lower housing and on the upper I cut off the cone inside the housing and filled it flat. iInstalled my thermostat and gasket, refilled coolant and have never had another problem.


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