my 02 vette was overheating..it blew out coolant twice....i never figured out what caused it....i repaced the thermostat..water pump..coolant..temp sensor..fushed the radiator...blew out and washed out the radiator and a/c condensor...now i'm getting false temp readings..false overheating..up to 263 degrees showing on the analog and dic read out..the problem is intermittant..the temp spikes all the way up..cooling fans on high..bells and whistles..but the car is not actually overheating...engine oil temp on dic showing normal and trans fluid... i have been checking it with an infared temp gun...i can't find anything over 212 degrees...even after driving at speeds up to 75 mph..and pointing the temp gun directly at the temp sensor..212 degrees..also...the car even goes to reduced power...it seems now that i have a vibration at 1500 rpm..or under acceleration...i'm thinking it may be..from the engine going to to reduced power and alternating cylinder firing..gas fouling a plug...changing the plugs is easy enough...has anyone else had this had..or having this problem...or does anyone have an idea about how to correct it?...short of going to the dealer?

 

Check your codes ... you probably have a P1258 set for engine overheating.

Sounds like the Engine Coolant Temperature (ECT) sensor has failed. It is easy to replace. It is located in the head, just above the #1 spark plug (front of engine, drivers side).

Disconnect the electrical connection to it, unscrew the sensor, screw in the new one, and connect the electrical connection to it ...

Some notes:

You may want to drain some coolant from the system before removing the sensor, otherwise when you take the old one out be prepared for coolant to run out.

The new sensor should come with a sealer on the threads, or packaged with it. (sealer is GM Part 12346004

The GM part number for the sensor is 15326388 and can be bought from one of the supporting vendors for around $20 to $25

Torque for installing is 15 lb ft

 

I'm guessing when you flushed out your radiator you got some water on your PCM. Pull your battery out and check all your connections to the computer. Its also possible that someone gave you a bad temp sensor.

 

i have already replaced the temp sensor new from the dealer

 

what is the pcm?

 

If the engine is running at 212 and the PCM (Powertrain Control Module - the engine/transmission control computer) is reporting that the engine temp is 263, there are only two possible sources for the problem ...

1) Bad ECT sensor. The sensor is wired directly to the PCM. The PCM then reports data such as engine RPM and ECT on the data bus for other computers (such as the IPC - the computer that controls your gauges and DIC) to use.

2) Bad wiring or a bad connection between the ECT sensor and the PCM.

The ECT sensor is quite sensitive, and has to be handled with care. Dropping it, for example, will dramatically increase the chance that the sensor won't work correctly. There is a WARNING in the service manual to this effect.

 

I would also check to make sure you have purged all the air out of the cooling system. You could have and air pocket near the sensor. Also while you replaced everything, replace the cap too.

 

With the engine running (but not hot) check the coolant reservoir for bubbles... I hate to say it, but you could have a blown head gasket.