Chart C-12 Coolant Fan Functional Check

Chart C-12:

Chart C-12 Wiring Diagram:

CIRCUIT DESCRIPTION:

Battery voltage to operate the cooling fan motor is supplied to relay terminal "1". Ignition voltage to energize the relay is supplied to relay terminal "5". When the ECM grounds CKT 335, the relay is energized and the cooling fan is turned "ON". When the engine is running, the ECM will turn the cooling fan "ON" if the conditions for a coolant temperature sensor trouble code (Code 14 or 15) are present or the A/C is "ON," or the coolant temperature is greater than 108~C (230~F).


DIAGNOSTIC AIDS:

^ If the owner complained of an overheating problem, it must be determined if the complaint was due to an actual boilover, or the hot light, or temperature gauge indicated over heating.

^ If the gauge, or light, indicates overheating, but no boilover is detected, the gauge circuit should be checked. The gauge accuracy can, also, be checked by comparing the coolant sensor reading using "Scan" tool and comparing its reading with the gauge reading.

^ If the engine is actually overheating, and the gauge indicates overheating, but the cooling fan is not coming "ON", the coolant sensor has probably shifted out of calibration and should be replaced.

^ If the engine is overheating, and the cooling fan is "ON", the cooling system should be checked.