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The service code P1126 on your Nissan indicates a faulty thermostat, not a relay of any kind.
If you would like to test your thermostat before replacing it, perform the following operations.
Get a pot of water heating on a stove, suspend the thermostat in the water by tying it to something that can hang across the top of the pot with some ordinary string, use a thermometer (one that can at least stand the boiling point of water which is 212 degrees farenheit). Put the thermometer in the water along with the setup and watch the temperature. At around 190 degrees, the thermostat should open up indicating that it operates normally. If not, then it is defective, or it is rated to open at a different temperature. There is usually a stamp or engravement at the butt of the thermostat that shows its temperature rating.
If the tets proves the thermostat is working properly, replace the defective engine coolant temperature (ECT) sensor.
Hope this helps.
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Friday, January 9th, 2009 AT 7:51 PM