GM Service Manual Online
For 1990-2009 cars only

The engine coolant level module is located in the radiator's right side tank and monitors the engine coolant level. Ground is applied at all times from G113 to the engine coolant level module through circuit 451. When the coolant level falls below an acceptable level, the module acts like a switch and closes. Ground is then applied from the module through circuit 68 to the IPC. The instrument panel cluster illuminates the LOW COOLANT LEVEL message.