ELECTRICAL SYSTEM TESTS, INSPECTIONS, AND ADJUSTMENTS - CONTINUED
ENGINE FAN CONTROL SOLENOID CIRCUIT TEST
N OT E
Use this procedure to troubleshoot any suspectproblems with engine fan control solenoid for
engine cooling fan.
This procedure covers folowing diagnostic codes:
291-05 Engine Cooling Fan Solenoid Open Circuit
291-06 Engine Cooling Fan Solenoid Short to Ground
ECM controls speed of engine coolin fan to provide following benefits:
Improved fuel economy.
Reduced overcooling of engine.
ECM monitors engine coolant temperature, inta e manifold air temperature, and hydraulic oil
temperature to determine correct speed for engine cooling fan.
ECM controls fan speed by controlling current to engine fan control solenoid. As current to con-
trol solenoid is changed, angle of fan pump's swashplate changes proportionally. This changes
output of hydraulic oil from fan pump to cooling fan.
If ECM detects a system fault, ECM provides minmum current to solenoid. This ensures a maxi-
mum fan speed while fault condition exists.
An override is available with ET This allows fan to be manually changed from minimum to max-
imum possible rpm.
Inspect electrical connectors and wiring. Refer to Electrical Connector Inspection (WP 0022 00).
Place battery disconnect switch in OFF position (TM 5-3805-291-10).
Perform 10 lb (45 N) pull test on each wire in ECM connectors associated with ECM power supply.
Check J2/P2 ECM connector (socket-head screw) for proper torque of 60 lb-in. (7 Nm).
Check J1/P1 ECM connector (socket-head screw) for proper torque of 55 lb-in. (6 Nm).
Check harness and wiring for abrasion and pinch points from sensors back to ECM.