SPACER 1378479 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the electrical system if a problem is suspected with the desired speed input or if one of the diagnostic codes in Table 1 is active.
Table 1
Diagnostic Codes Table    
Code    Conditions which Generate this Code    System Response    
524-3 Desired Engine Speed Sensor : Voltage Above Normal     The Electronic Control Module (ECM) has been powered up for at least five seconds. The current to the ECM for the desired speed input is greater than 22 mA for more than five seconds.     When the "Idle/Rated" switch is in the "Rated" position, the ECM assumes a default value for the desired engine speed.
The default value for the desired engine speed is equal to the "Minimum Engine High Idle Speed" that is programmed on the "Service/Configuration" screen of Caterpillar Electronic Technician (ET).
The alarm output is activated. The code is logged.    
524-4 Desired Engine Speed Sensor : Voltage Below Normal     The ECM has been powered up for at least five seconds. The current to the ECM for the desired speed input is less than 2 mA for more than five seconds.    Note: For this troubleshooting procedure, the "Desired Speed Input" configuration parameter must be set to "4-20 mA Input" in the "Service/Configuration" screen of Cat ET. The selection of this setting requires a 4 to 20 mA signal for regulation of the desired engine speed. If the "Desired Speed Input" is set to "0-5 VDC Input", do not use this procedure to troubleshoot the circuit.When the desired speed input is correspondingly configured, the ECM controls the engine speed according to the 4 to 20 mA current.The value of the current corresponds to a range of desired engine speeds between minimum high idle and maximum high idle. The "Minimum Engine High Idle Speed" and the "Maximum Engine High Idle Speed" are set with the "Service/Configuration" screen of Cat ET. For more information, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".When the "Idle/Rated" switch is in the Rated position, a current value of 4.0 mA corresponds to the programmed "Minimum Engine High Idle Speed". A current value of 20.0 mA corresponds to "Maximum Engine High Idle Speed". Current values within this range will vary the desired engine speed in a linear fashion between "Minimum Engine High Idle Speed" and "Maximum Engine High Idle Speed".The ECM will generate a diagnostic code in response to current outside of the range of 4 to 20 mA.Current values that are greater than 22 mA will activate the "524-3 Desired Engine Speed Sensor short to +batt" diagnostic code. Current values that are less than 2 mA will activate the "524-4 Desired Engine Speed Sensor short to ground" diagnostic code. The most likely causes of the diagnostic code are a poor connection or a problem in a wiring harness. The next likely cause is a problem with a component. The least likely cause is a problem with the ECM.Logged diagnostic codes provide a historical