2003 Saturn ION "Coolant" light

popi asked:
2003 Saturn ION "Coolant" light
2003 Saturn ION 2.2L engine, the coolant light started coming on.  No overheating and from other posts it would seem it was the sensor or thermostat.  Well being over achiever I : flushed and changed fluid, i replaced temp sensor, replaced thermostat, and changed radiator hoses.  Still not over heating, has fuild filled approriatately.  However, when start car coolant light come on.  If i press the dash reset button goes off and does not come back on until next time shut off car and restart.  What else could it be? What am I missing here?   Thanks in advance.

Answered By Justin Cupler, Contributing Writer:
Sounds to me like the famous GM coolant level sensor. This little gem is located in the coolant reservoir tank and is famous for failing, thanks to Dex-Cools congealing problem--which supposedly doesn't exist. This sensor, unfortunately, is part of the coolant reservoir and it must be replaced with the reservoir only. 

There is a quick test to make certain this is the problem. Bend a paper clip in  a U-shape, unplug the wiring harness from the sensor at the bottom of the reservoir and jumper the two electrodes together in the harness. This "completes the circuit" and will turn the light off if the sensor is the problem. 

If the light stays off for a few days, you can either replace the entire reservoir or simply leave the jumper attached and periodically check your fluid.    
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