COUPLING-PERMANENT 1241961 - Caterpillar

System Operation Description:Use this procedure to troubleshoot suspect problems with the circuit for the sensor supplies.This procedure covers the following diagnostic codes:
41-3 8 Volt DC Supply : Voltage Above Normal
41-4 8 Volt DC Supply : Voltage Below Normal
145-3 12 Volt DC Power Supply : Voltage Above Normal
145-4 12 Volt DC Power Supply : Voltage Below Normal
262-3 5 Volt Sensor DC Power Supply : Voltage Above Normal
262-4 5 Volt Sensor DC Power Supply : Voltage Below NormalThe Electronic Control Modules (ECM) supply operating voltage to the engine's sensors. Refer to Illustration 1 for details.Note: Terminals J1-2 and J1-18 are connected together inside the ECM. A short circuit on one of these terminals will cause a short circuit on the other terminal.The most likely cause of a diagnostic code are a poor connection or a problem in a wiring harness. The next likely cause is a problem with a sensor. The least likely cause is a problem with the ECM.Logged diagnostic codes provide a historical record. Before you begin this procedure, use Caterpillar Electronic Technician (ET) to print the logged codes to a file.This 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."DESIRED SPEED" Potentiometer (if equipped)The ECM provides 5.0 0.5 VDC to the "DESIRED SPEED" potentiometer (if equipped).A 262-3 diagnostic code is activated if both of these conditions occur:
The desired speed signal wire is shorted to a voltage source that is greater than +5 volts.
The "DESIRED SPEED" potentiometer is near the maximum desired speed or at the maximum desired speed.A 262-4 diagnostic code is activated if both of these conditions occur:
The desired speed signal wire is shorted to ground.
The "DESIRED SPEED" potentiometer is near the maximum desired speed or at the maximum desired speed.Illustration 1 is the schematic diagram for the operating voltage to the sensors. If the optional Auxiliary Sensing Module is not installed, the air inlet pressure sensor is connected to the ECM.
Illustration 1 g01325468Test 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 connectors:
ECM connectors
Connectors on the terminal box
Check the torque of the allen head screws for the ECM connectors.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuits for the sensors.
Check the harness and wiring for corrosion, for abrasion and for pinch points from each sensor to the ECM. Expected Result:All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.Results:
OK - All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points. The components are in good condition with proper connections. If you are troubleshooting a problem with the 5 volt supply for the ECM, proceed to Test Step 2. Otherwise, proceed to Test Step 4.
Not