PIPE 1175612 - Caterpillar

System Operation Description:Use this procedure to troubleshoot the following diagnostic codes:
41-3 8 Volt DC Supply voltage above normal
41-4 8 Volt DC Supply voltage below normalThe Electronic Control Module (ECM) supplies 8.0 0.8 VDC to the following sensors:
Sensor for engine coolant pressure (outlet)
Sensor for inlet air pressure
Both of the detonation sensorsAn active 41-3 or 41-4 diagnostic code is probably caused by a short circuit or an open circuit in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with the ECM.This troubleshooting procedure may generate additional diagnostic codes. Continue troubleshooting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.
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Schematic for the 8 volt supplyTest Step 1. Inspect the Electrical Connectors and the Wiring
Set the engine control to the OFF/RESET position.Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
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Location of the sensors for the sensor supply circuit (typical front engine view) (1) Inlet air pressure sensor
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Location of the sensors for the sensor supply circuit (typical top engine view) (2) Engine coolant pressure sensor (outlet)
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Location of the sensors for the sensor supply circuit (typical right side engine view) (3) Detonation sensor
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Location of the ECM connectors for the sensor supply circuit (typical left front engine view) (4) J2/P2 ECM connectors (5) J1/P1 ECM connectors
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Location of the engine interface connectors for the sensor supply circuit (typical left rear engine view) (6) Engine interface connectors
Thoroughly inspect the connectors for sensors (1), (2), and (3). Also, thoroughly inspect ECM connectors (4) and (5), and interface connector (6) .
Check the allen head screws for each of the ECM connectors for the proper torque.
Check the harness and wiring for abrasion and for pinch points from each 8 volt sensor to the ECM.Expected Result:All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.Results:
OK - All of the 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. Proceed to Test Step 2.
Not OK - At least one of the connectors, pins, and sockets are not connected properly. At least one of the connectors and/or the wiring has corrosion, abrasion, and/or pinch points.Repair: Perform the necessary repairs and/or replace parts, if necessary.STOPTest Step 2. Check for Diagnostic Codes
Establish communication between Cat ET and the engine ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
Set the engine control to the STOP position.
Observe the "Active Diagnostic" screen on Cat ET. Wait at least 30 seconds so that any codes may become activated. Look for these codes:
41-3 8 Volt DC Supply : Voltage Above Normal
41-4 8 Volt DC Supply : Voltage Below Normal
Observe the "Logged Diagnostic" screen on Cat ET. Look for the same codes.Expected Result:The 41-3 code or the 41-4 code is not active.Results:
No codes - The 41-3 code or the 41-4 code is not