866461A02 Mercruiser COVER ASSEMBLY, Top

Table 1
Diagnostic Codes Table    
CDL Code and Description    Conditions which Generate this Code    System Response    
291-5 Engine Cooling Fan Solenoid current below normal     The Electronic Control Module (ECM) detects an open circuit and/or a short to the +Battery in the circuit for the cooling fan control solenoid.     The ECM sends minimum current to the fan control solenoid. The code is logged.    
291-6 Engine Cooling Fan Solenoid current above normal     The ECM detects a short circuit to ground in the circuit for the cooling fan control solenoid.    
Illustration 1 g02307434
Location of the cooling fan control solenoid (left rear engine view) (1) Pump (2) Cooling fan control solenoidThe ECM controls the rpm of the engine fan in order to provide the following benefits:
Increased productivity
Reduced noise from the fan
Improved fuel economy
Reduced overcooling of the engineThe fan control solenoid controls the displacement of the hydraulic pump that supplies pressurized oil to the fan motor. The ECM controls the speed of the fan by controlling the current to the fan control solenoid. The current to the cooling fan control solenoid varies between 0.12 (maximum fan rpm) to 1.30 A (minimum fan rpm). The fan is controlled to maintain a speed between 485 (minimum fan rpm) to 1107 rpm (maximum fan rpm). The ECM continuously adjusts the current to the cooling fan control solenoid. This control ensures that the fan rpm remains within 50 rpm of the desired rpm. The engine cooling fan pump pressure sensor provides feedback to the ECM about the hydraulic oil pressure that is available at the fan pump. The ECM compares this feedback signal to a set of maps that are stored in the software. The maps are used by the ECM to calculate the desired fan drive pump pressure. If the actual pump pressure is different from the calculated pressure, the ECM will vary the current to the cooling fan control solenoid. The ECM controls the pump pressure to match this calculated pressure.Cooling fan control is suspended until the following conditions are met:
Engine coolant temperature is greater than 90° C (194° F)
Outlet temperature of the ATAAC is greater than 50° C (122° F)
Hydraulic oil temperature is greater than 90° C (194° F)During cooling fan control, the following conditions are targeted by the engine ECM:
An engine coolant temperature that is equal to 104° C (219° F)
An outlet temperature for the ATAAC that is equal to 55° C (131° F)
A hydraulic oil temperature that is equal to 95° C (203° F)The ECM monitors engine coolant temperature and intake manifold air temperature in order to determine the correct fan rpm. When a system fault is detected, fan rpm is increased. When the engine is lugging, the fan rpm is reduced in order to reduce the load on the engine. The speed of the fan is also reduced during high altitude operation.An override is available with Caterpillar Electronic Technician (ET). The override allows the fan to be manually changed from the minimum to the maximum rpm. If the ECM detects a problem with the solenoid circuit, a diagnostic code is generated. If the ECM detects a system fault, the ECM provides minimum current to the solenoid. This current ensures a maximum fan speed while the fault condition exists. The ECM will generate diagnostic code for the fault.
Illustration 2 g01415855
Schematic for the cooling fan control solenoidTest Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 3 g02307595
Location of the J1/P1 ECM connectors
Thoroughly inspect the J1/P1 ECM connectors. Inspect all of the other connectors that are in the circuit for the cooling fan control solenoid. Refer to Troubleshooting, "Electrical Connectors - Inspect".
Illustration 4 g01415857
P1 ECM connector (P1-43) Cooling fan control solenoid (P1-51) Solenoid return
Illustration 5 g01155187
Terminal locations at the connector for the cooling fan control solenoid (Terminal 1) Power to the solenoid (Terminal 2) Return
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the allen head screw on each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points.Expected Result:All connectors, pins, and sockets are coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and wiring appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem in the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Check for Active Diagnostic Codes
Connect Cat ET to the service tool connector.
Turn the keyswitch to the ON position.
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Select diagnostic tests from Cat ET.
Select the "Override Parameters" screen on Cat ET.
Activate the fan override.
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.Note: Wait at least 30 seconds in order for the diagnostic code to become active.
Disable the fan override.
Determine if the problem is related to an open circuit diagnostic code -5 or a short circuit diagnostic code -6.Expected Result:No diagnostic codes are active.Results:
OK - No diagnostic codes are active.Repair: The problem may have been related to a faulty connection in the harness. Carefully inspect the connectors and wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - A short circuit diagnostic code -6 is active at this time. Proceed to Test Step 3.
Not OK - An open circuit diagnostic code -5 is active at t