Part 3 of 4

Chart C-12 (3 Of 4):

Cooling Fan Circuit:

CIRCUIT DESCRIPTION
The cooling fans are controlled by the Powertrain Control Module (PCM) based on various inputs. The PCM controls the low speed cooling fan operation by grounding CKT 335. When the low speed relay #1 is energized, the ground path for the left hand coolant fan is through the series/parallel relay #2, then through the right hand coolant fan. Since the fans are connected in series, they both run at low speed. During high speed fan operation, all three cooling fan relays are energized connecting the fans in a parallel circuit. This results in both fans operating at high speed.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. Checks for a faulty #2 fan relay.
2. Checks for an open in CKT 409.
3. Checks for an open in CKT 1350 or a faulty #2 fan motor.

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 warning indicator light, or engine coolant temperature gage indicated overheating.
If the engine is overheating and the cooling fans are "ON," the cooling system should be checked.
The PCM will command low speed fans "ON" at 106°C (223T) and "OFF" at 102°C (216°F) and, high speed fans "ON" at 110°C (230°F) and "OFF" at 105°C (221°F).