GEAR-RING 9P3555 - Caterpillar

Use this procedure when the following diagnostic codes are active:
544-08 Engine Cooling Fan Speed signal abnormal
544-02 Engine Cooling Fan Speed Sensor Loss of SignalThe engine cooling fan speed sensor provides a signal to the Electronic Control Module (ECM). The ECM controls fan speed by varying the current to the fan control solenoid.The engine cooling fan speed sensor receives a supply voltage of 8.0 0.5 VDC from the ECM. The sensor outputs a frequency that is directly proportional to fan speed. The sensor generates a signal pulse for each revolution of the fan. The output frequency varies between 5 Hz to 180 Hz over the speed range between 50 rpm and 1800 rpm.
Illustration 1 g01224568
Schematic for the fan speed sensor
Test Step 1. Inspect Electrical Connectors and Wiring
Remove the electrical power from the ECM.
Illustration 2 g01146374
Left side engine view (typical example)
(1) J1/P1 ECM connector
Illustration 3 g01183942
Engine cooling fan assembly (typical example)
(2) Engine cooling fan speed sensor connector
(3) Cooling fan drive assembly
Thoroughly inspect connectors (1). Also, thoroughly inspect connector (2) that is for the integral components of fan drive (3). Refer to the