The coolant level switch notifies the second-generation, onboard diagnostic system (OBD-II) when your radiator becomes low on coolant. Over time, this sensor can become corroded and stop working properly. As a result, if your Saturn's radiator develops a leak, your OBD-II may not indicate a problem. Coolant could run out of the radiator, which could warp the engine block as a result of overheating. All Saturns since the 1996 model year utilize OBD-II for diagnostics, so the process for troubleshooting the coolant level switch is the same for any Saturn built since then.
Drive your Saturn onto a set of ramps. Secure the parking break. Open the engine hood. Allow the Saturn time to cool.
Place a clean drain pan under the petcock on the lower side of the radiator. Open the petcock with a pair of pliers, and drain approximately two gallons of fluid into the pan. Close the petcock with the pliers.
Start the Saturn's engine. Wait approximately five minutes for the "Coolant" light to illuminate. If the light does not illuminate within five minutes, the coolant level switch is defective. If the light does illuminate, immediately turn off the vehicle. Saturn radiators hold approximately six gallons of coolant, and you will not damage the vehicle by running it with four gallons of fluid for five minutes.
Open the lid on the overflow expansion tank located on the left side of the radiator. Place a funnel into the hole. Pour the coolant back into the radiator. Close the cap.
