811611 Mercury COVER

Table 1
Diagnostic Codes Table
CDL Code Code Description Comments
291-5 Engine Cooling Fan Solenoid:Current Below Normal The code is logged.
The Electronic Control Module (ECM) forces the cooling fan to maximum speed.
291-6 Engine Cooling Fan Solenoid:Current Above Normal
Illustration 1 g02264394
Fan control solenoid
The ECM controls the speed of the fan by controlling the current to the fan control solenoid. The fan control solenoid controls the displacement of the hydraulic pump that supplies pressurized oil to the fan motor. If the ECM detects an open or a short in the solenoid circuit, the fan pump defaults to maximum pressure. When the fan pump produces maximum pressure, the fan speed is maximum.The cooling fan speed sensor provides feedback to the engine ECM. The ECM uses the feedback from the sensor to compare the actual fan speed to the desired fan speed. The ECM controls fan speed by varying the current to the fan control solenoid. The ECM controls fan speed within 50 rpm of the desired fan speed.The ECM controls the rpm of the engine fan in order to provide the following benefits:
Increased machine productivity
Fan noise reduction
Improved fuel economy
Reduction of engine overcoolingThe ECM monitors engine coolant temperature and intake manifold air temperature to calculate a correct fan rpm. When the engine is lugging, the fan rpm is reduced in order to reduce the load on the engine.An override for the cooling fan feature is available in Caterpillar Electronic Technician (ET). The override allows for manual control of the fan speed 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 problem with the solenoid circuit, the current to the solenoid is set to the minimum value.
Illustration 2 g02154155
Schematic for the engine cooling fan circuit
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the ECM.
Illustration 3 g02133295
(1) Location of the J1/P1 ECM connectors
Illustration 4 g02154194
Location of the cooling fan control solenoid (left front machine view)
Thoroughly inspect ECM connector (1) and the connector for the engine fan control solenoid. Inspect all of the other connectors that are in the circuit. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
Illustration 5 g02154197
P1 ECM connector
(P1-43) Fan solenoid
(P1-51) Return
Illustration 6 g01155187
Connector for the fan control solenoid
(Terminal 1) Signal
(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 for each ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
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 are 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.
Restore the electrical power to the ECM.
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.
Determine if the problem is related to a low current diagnostic code (-5) or a high current 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 reinspect the connectors and wiring. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - A low current diagnostic code (-5) is active at this time. Proceed to Test Step 4.
Not OK - A high current diagnostic code (-6) is active at this time. Proceed to Test Step 3.Test Step 3. Disconnect the Connector for the Cooling Fan Control Solenoid in Order to Create an Open Circuit
Remove the electrical power from the ECM.
Disconnect the connector for the fan control solenoid.
Restore the electrical power to the ECM. Wait at least 30 seconds for activation of the diagnostic codes.
Access the "Active Diagnostic Code" screen on Cat ET. Check for an active low current diagnostic code (-5) for the engine fan control solenoid.
Remove the electrical power from the ECM. Expected Result:A low current diagnostic code (-5) is now active for the engine fan control solenoid.Results:
OK - A high current diagnostic code (-6) was active before disconnecting the connector. A low current diagnostic code (-5) became active after disconnecting the connector.Repair: Temporarily connect a new fan control solenoid to the harness, but do not install the new fan control solenoid. Verify that there are no active diagnostic codes for the solenoid. If there are no active diagnostic codes for the solenoid, permanently install the new solenoid. Clear any logged diagnostic codes.STOP
Not OK - The high current diagnostic code (-6) remained active after disconnecting the connector. There is a short circuit between the solenoid harness con