ELBOW 1446650 - Caterpillar

System Operation Description:The throttle position sensor (TPS) eliminates the mechanical throttle and governor linkages. The TPS utilizes the lever movement by the operator to send an electrical signal to the Electronic Control Module (ECM) for the engine. The signal from the TPS and the signal from the speed/timing sensors are processed by the ECM in order to control the engine speed.The direct fuel control replaces the throttle position sensor when an external governor is used. An electrical converter converts the 0 to 200 mA current from the governor into a pulse width modulated signal that can be used by the ECM. The use of the direct fuel control will disable the governing strategy and speed controlling strategy of the engine software.Test Step 1. Identify the Speed Control System that is UsedDetermine if a throttle position sensor, direct fuel control, or J1939 throttle is being used to control engine speed.Expected Result:The desired engine speed is controlled with a throttle position sensor, direct fuel control, or J1939 throttle.Results:
Throttle Position Sensor - A throttle position sensor is used to control engine speed. Proceed to Test Step 2.
Direct Fuel Control - Direct fuel control is used to control engine speed. Proceed to Test Step 10.
J1939 Throttle - The J1939 data link is utilized for desired engine speed.Repair: Verify that the "Desired Speed Input Configuration" parameter is programmed to "CAN Input". Also verify that the "Throttle Position Sensor" parameter is programmed to "Not Installed" and verify that the "Direct Fuel Control Mode" parameter is programmed to "Disabled".Refer to Troubleshooting, "CAN Data Link Circuit - Test".STOPTest Step 2. Check Programmable Parameters
Connect the Caterpillar Electronic Technician (ET) to the data link connector.
Turn the keyswitch to the ON position.
Verify that the "Throttle Position Sensor" parameter is programmed to "Installed". Also, verify that the "Direct Fuel Control Mode" parameter is programmed to "Disabled" and verify that the "Desired Speed Input Configuration" parameter is programmed to "PWM".Expected Result:The parameters are programmed correctly.Results:
OK - The parameters are programmed correctly. Proceed to Test Step 3.
Not OK - The parameters are not programmed correctly.Repair: Program the parameters.Verify that the repair eliminates the problem.STOPTest Step 3. Inspect Electrical Connectors and Wiring
Illustration 1 g00923431
Schematic for throttle position sensor
Illustration 2 g00763651
Electronic throttle position sensor
Illustration 3 g00763656
Lever operated throttle position sensor"Stops" for the lever are set to "Low idle" and "High idle".
Illustration 4 g00763658
Throttle position sensor with adjustment knobUse a CCW rotation for two turns for "High idle" and use CW rotation for two turns for "Low idle". Pushing the knob "IN" will also return the engine to "Low idle".
Table 1
Pin Assignment on the Sensor     Connection    
Pin A     Switched positive battery    
Pin B     Negative battery on bus bar    
Pin C     Throttle position signal    The output of the sensor is a constant frequency signal with a pulse width that varies with the throttle position. The pulse width measures the duty cycle. The Pulse Width Modulated signal (PWM) is expressed as a percentage of the duty cycle. This percentage is between 0 and