Pontiac Fiero 1988 Service Manual page 575

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6E2-C12-2 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI)

HARNESS CONNECTOR

(FUSIBLE LINK).

DK GRN/WHT 335

TEMP. SIGNAL

ENGINE COOLING PAN-

SERIES (TBI)

Circuit Description:

Battery voltage to operate the cooling fan motor is supplied to relly terminal "A". Ignition voltage to

energize the relay is supplied to relay terminal "D". 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:

• A/C is "ON" and vehicle speed is less than 30 mph (48 Km/h).

• Coolant temperature greater than 1 0 8 ° C (230°F).

® Code 14 or 15, coolant sensor failure.

Diagnostic Aids:

If the owner complained of an overheating

problem, it must be determined if the complaint was

due to an actual boil over, or the hot light, or temp,

gage indicated over heating.

If the gage, or light, indicates overheating, but no

boilover is detected, the gage circuit should be

checked. The gage accuracy can, also, be checked by

comparing the coolant sensor reading using a "SCAN"

tool and comparing its reading with the gage reading.

If the engine is actually overheating and the gage

indicates overheating, but the cooling fan is not

coming on, the coolant sensor has probably shifted out

of calibration and should be replaced.

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