CLAMP 2396808 - Caterpillar

System Operation Description:Use this procedure to troubleshoot suspect problems with the circuit for the "4-20 mA Input".This procedure covers the following diagnostic codes:
524-3 Desired Engine Speed Sensor : Voltage Above Normal
524-4 Desired Engine Speed Sensor : Voltage Below NormalNote: For this troubleshooting procedure, the "Desired Speed Input" configuration parameter must be set to "4-20 mA Input" in the "Service/Configuration" screen of Caterpillar Electronic Technician (ET). Do not select "PWM". The Electronic Control Module (ECM) cannot be configured to accept a PWM input signal for control of the engine speed.The selection of the "4-20 mA Input" 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".Current values that are greater than 22.0 mA will activate the 524-3 diagnostic code. Current values that are less than 2.0 mA will activate the 524-4 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 record. Before you begin this procedure, use Cat ET to print the logged codes to a file.The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.
Illustration 1 g01325630
Schematic of the 4 to 20 mA desired speed input
Test Step 1. Inspect the Electrical Connectors and Wiring
Remove the electrical power from the engine. Note: For the following steps, refer to Troubleshooting, "Electrical Connectors - Inspect".
Thoroughly inspect the following components:
J1/P1 connectors
J6/P6 connectors
Wiring and the connections between the terminal box and the device that supplies the 4 to 20 mA signal
Check the torque of the allen head screw for the ECM connectors.
Check the harness and wiring for abrasion and for pinch points between the device that supplies the 4 to 20 mA signal and the ECM. Expected Result:All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion,