Cutlass L4-138 2.3L VIN A FI HP (1990)
Chart C-12 Wiring Diagram
***UPDATED BY TSB # 90-T-180 DATED NOVEMBER 1990
CIRCUIT DESCRIPTION:
Each electric coolant fan is controlled by the ECM through the fan relay based on inputs from the coolant temperature sensor, manifold air temperature,
the A/C control switch, A/C pressure sensor and the vehicle speed sensor. The ECM controls the coolant fan by grounding circuit 702 and or circuit 532
which turns "ON" the respective fan relay.
The primary fan relay will be commanded "ON" when any one of the following conditions exist:
^
Coolant temperature 103~C - 106~C or more.
^
A/C clutch energized and vehicle speed is less than 35 mph.
^
Any fault causing the SERVICE ENGINE SOON light to be "ON" is present.
The secondary fan relay (if equipped) will be commanded "ON" when:
^
Coolant temperature 115~C - 118~C or more.
^
A/C pressure is high.
NOTE: The secondary cooling fan may be commanded "ON" when the ignition is turned "OFF".
TEST DESCRIPTION:Numbers below refer to circled numbers on the diagnostic chart.
1.
With the Field Service Mode activated, the coolant fan(s) control driver(s) should close, which should energize the fan(s) control relay(s).
2.
Test to see if fault is in wiring to the fan or the fan/fan connection.
DIAGNOSTIC AIDS:
^
If equipped with two fans, and both are inoperative, check for open circuit 2 or 150 first.
^
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 temperature gauge indicated overheating.
^
If the gauge, or light, indicates overheating, but no boil over is detected, the gauge or light circuit should be checked, The gauge accuracy can
also be checked by comparing the coolant sensor reading using a "Scan" tool with the reading of the gauge.
^
If the engine is actually overheating, and the gauge indicates overheating, but the coolant fan is not coming "ON", the coolant sensor has
probably shifted out of calibration and should be replaced. See Code 15 chart for a temperature to resistance chart.
