Diagnostic Aids

If an overheating condition is suspected, verify if it is due to an actual boilover. If gauge or light indicates an overheat condition and boilover is not evident, inspect gauge circuit for malfunction.

If vehicle is overheating and gauge or light indicates so but cooling fan is not coming on, check coolant sensor temperature using a Tech 1 scan tester. Sensor may have shifted out of calibration and should be replaced. If engine is overheating and cooling fan is on, check cooling system.

Fig 1: Chart C-12 Schematic (3.1L "J" Body) Cooling Fan Circuit Diagnosis

Courtesy of GENERAL MOTORS CORP.

Fig 2: Chart C-12 Flow Chart (1 Of 2)(3.1L "J" Body) Cooling Fan Circuit Diagnosis

Courtesy of GENERAL MOTORS CORP.