SEAL-RING 2892938 - Caterpillar

System Operation Description:The master Electronic Control Module (ECM) supplies 8.0 0.8 VDC to these sensors:
Sensor for engine coolant pressure (outlet)
Sensor for inlet air pressure
Sensor for atmospheric pressure
Sensor for boost pressure
The detonation sensors for the left side of the engineThe slave ECM supplies 8.0 0.8 VDC to the detonation sensors for the right side of the engine.Terminals J1-4, J2-56, and J2-57 are connected together inside the master ECM. A short circuit on one of these terminals will cause a short circuit on the other terminals.A "+8 V sensor supply" diagnostic code is probably caused by a short circuit or by an open circuit in a harness. The next likely cause is a sensor problem. The least likely cause is a problem with an ECM.Logged diagnostic codes provide a historical record. Before you begin this procedure, use the 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.
Illustration 1 g01090688
Schematic for the 8 volt sensors that are powered by the master ECM
Illustration 2 g01085615
Schematic for the 8 volt sensors that are powered by the slave ECMTest Step 1. Inspect the Electrical Connectors and Wiring
Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
Illustration 3 g01085778
Terminal box for the master ECM (1) J2/P2 connectors for the master ECM (2) J1/P1 connectors for the master ECM (3) J6/P6 connectors for the harness to the detonation sensors on the left side of the engine (4) J7/P7 connectors for the harness to the 8 volt sensors
Illustration 4 g01085783
Terminal box for the slave ECM (5) J4/P4 connectors for the slave ECM (6) J12/P12 connectors for the harness to the detonation sensors on the right side of the engine
Thoroughly inspect each of the following connectors:
J1/P1 and J2/P2 connectors for the master ECM
J6/P6 and J7/7 connectors on the terminal box for the master ECM
J4/P4 connectors for the slave ECM
J12/P12 connectors on the terminal box for the slave ECM
Check the torque of the allen head screw for the ECM connectors. The proper torque is 6 1 N m (55 9 lb in).
Illustration 5 g01085970
Harness side of the master ECM P1 connector (P1-4) 8 volt supply for the pressure sensors
Illustration 6 g01085973
Harness side of the master ECM P2 connector (P2-56) 8 volt supply for the detonation sensors (P2-57) 8 volt supply for the detonation sensors
Illustration 7 g01085976
Harness side of the P6 connector (P6-F) 8 volt supply for the detonation sensors (P6-J) 8 volt supply for the detonation sensors
Illustration 8 g01085986
Harness side of the P7 connector (P7-N) 8 volt supply for the boost pressure sensor (P7-O) 8 volt supply for the sensor for atmospheric pressure (P7-T) 8 volt supply for the sensor for the engine coolant pressure (outlet) (P7-j) 8 volt supply for the sensor for inlet air pressure
Illustration 9 g01085973
Harness side of the P4 connector for the slave ECM