825123A 1 Mariner GEAR HOUSING

Table 1
Diagnostic Codes Table    
Description     Conditions which Generate this Code     System Response    
544-8 Engine Cooling Fan Speed Sensor : Abnormal Frequency, Pulse Width, or Period     The engine speed is equal to or greater than low idle but less than 2400 rpm for one minute.
The fan speed is less than 38 rpm or the fan speed is greater than 2000 rpm for two seconds.     The code is logged.    The fan speed sensor is a digital sensor that provides a speed signal from the engine cooling fan to the Electronic Control Module (ECM). The ECM controls the speed of the fan by varying the current to the fan speed solenoid. The ECM attempts to keep the fan within 50 rpm of the desired fan speed.The fan speed sensor receives a regulated 8.0 0.4 VDC supply voltage from the ECM. The fan speed sensor provides a pulse width modulated signal to the ECM that represents the speed of the fan. The frequency range of the output represents fan speeds from 50 rpm to 1800 rpm.There is a connector for a 3.3K Ohm pull-up resistor spliced into the harness near the sensor. The resistor is mounted near the cooling fan toward the front of the engine.Note: Refer to Troubleshooting, "Sensor Supply - Test" if the ECM has detected a problem with the digital sensor supply voltage.
Illustration 1 g03355674
Schematic for the fan speed sensorTest Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01234146
Location of ECM connectors
Thoroughly inspect ECM connector J1/P1, ECM connector J2/P2, and all other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g02593596
P2 terminals that are associated with the cooling fan speed (P2-56) 8V digital supply (P2-70) Engine fan speed
Illustration 4 g02593602
P1 terminals that are associated with the cooling fan speed (P1-60) Digital return
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the Cat Data Link.
Check the allen head screw on each ECM connector for the proper torque. Also, check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.Expected Result:All connectors, pins, and sockets are inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem with 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 the Status of the Engine Fan Speed with Caterpillar Electronic Technician (ET)
Turn the keyswitch to the OFF position.
Connect Cat ET to the service tool connector.
Turn the keyswitch to the ON position.
Access the "Fan Override Test" under the "Diagnostics" menu.
Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
Use a 1U-6602 Photo-Tachometer to determine the actual speed of the fan.
Compare the engine fan speed that is reported by Cat ET to the actual engine fan speed that is reported by the photo-tachometer.
Deactivate the "Fan Override Test".
Turn the keyswitch to the OFF position.Expected Result:The actual fan speed is within 50 rpm of the engine fan speed that is reported by Cat ET.Results:
OK - The engine fan speed is within the desired rpm range.Repair: The sensor is operating correctly. There may be an intermittent electrical problem in a connector or in the harness. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - The engine fan speed is not within the desired rpm range. Proceed to Test Step 4.Test Step 3. Check the Digital Sensor Supply Voltage at the Sensor Connector
Disconnect the connector for the engine cooling fan speed sensor.
Turn the keyswitch to the ON position.
Measure the voltage across terminal A (+8 V digital supply) and terminal B (sensor return).
Turn the keyswitch to the OFF position.Expected Result:The digital sensor supply voltage is 8.0 0.5 VDC.Results:
OK - The supply voltage is reaching the sensor. Proceed to Test Step 5.
Not OK - The supply voltage is not reaching the sensor. Proceed to Test Step 7.Test Step 4. Check the Resistance of the Cooling Fan Resistor
Remove the electrical power from the ECM.
Disconnect the cooling fan resistor at the harness connector for the resistor.
Measure the resistance of the resistor.Expected Result:The resistance of the cooling fan resistor is 3.3K Ohm.Results:
OK - The resistance of the resistor is 3.3K Ohm. The resistance of the resistor is within specifications. Reinstall the resistor. Proceed to Test Step 5
Not OK - The resistance of the resistor is not 3.3K Ohm.Repair: There is a problem with the cooling fan resistor. Replace the resistor.Verify that the original problem has been resolved.STOPTest Step 5. Check the Signal Frequency for the Engine Cooling Fan Speed Sensor at the Sensor Connector
Turn the keyswitch to the OFF position.
Remove the wire from terminal C (engine fan speed) on the sensor side of the connector for the engine cooling fan speed sensor. Connect the sensor connector.
Turn the keyswitch to the ON position.
Access the "Fan Override Test" under the "Diagnostics" menu on Cat ET.
Start the "Fan Override Test" on Cat ET. Set the fan speed to 800 rpm.
Use a multimeter to measure the frequency between the signal wire from the sensor and engine ground.
Deactivate the "Fan Override Test".
Turn the keyswitch to the OFF position.
Restore all connectors and wiring to the original configuration.Expected Result:The frequency is approximately 13 Hz.Results:
OK - The frequency is approximately 13 Hz. The engine cooling fan speed sensor is generating the correct signal. Return the wire to terminal 1 (engine fan speed) of the connector for the engine cooling fan speed sensor. Proceed to Test Step 6.
Not OK - The frequency is not approximatel