Diagnostic Aids

If cooling fans operate normally but an overheat condition exists, see COOLANT TEMPERATURE-TO-RESISTANCE VALUES table in CODE 15 chart in appropriate TESTS W/CODES article in this section. Replace coolant temperature sensor if mis-scaled. If coolant temperature sensor is okay, check for basic cooling system problem.

If coolant temperature exceeds 230°F (110°C) and manifold air temperature exceeds 102°F (39°C) with ignition off, ECM will energize cooling fans at low speed for up to 2 minutes or until coolant temperature is less than 210°F (99°C).

Fig 1: Chart C-12A Schematic (3.8L "W" Body) Cooling Fan Circuit Diagnosis

Courtesy of GENERAL MOTORS CORP.

Fig 2: Chart C-12A Flow Chart (1 Of 6)(3.8L "W" Body) Cooling Fan Circuit Diagnosis

Courtesy of GENERAL MOTORS CORP.