HOUSING-COMPRESSOR 6N7959 - Caterpillar

System Operation Description:This procedure tests whether proper voltage is supplied to the Electronic Control Module (ECM), to the Integrated Temperature sensing Module, and to the fuel metering valve. In addition to troubleshooting diagnostic codes, use this procedure if you suspect that the ECM, the Integrated Temperature Sensing Module, or the fuel metering valve are not receiving the proper supply voltage. The cause of an intermittent power supply can occur on either the positive side or on the negative side of the power supply.The 24 VDC power supply for the engine can be provided by a battery or by an electrical power supply. If the power is provided by an electrical power supply, the maximum allowable AC ripple is 150 mV AC peak to peak. The minimum requirement for the power supply is 22 VDC at 16 amperes. The wiring from the power supply to the component must provide a maximum voltage drop of 1.0 VDC. The power supply must be routed through a dedicated fuse or through a dedicated circuit breaker.Terminal P1-70 ("Switched +Battery") receives battery voltage from the engine control when the control is in the START mode, in the STOP mode, or in the AUTO mode. When the ECM detects battery voltage at this input, the ECM will power up. When battery voltage is removed from this input, the ECM will power down after the engine has shut down.The "168-02" diagnostic code indicates that the voltage of the power supply is intermittent or low while the engine is running. If the supply voltage drops to zero and stays at zero, the ECM will not log this code. The engine will shut down.The "336-02" diagnostic code indicates that the ECM has detected a problem with the circuit for the engine control switch.Logged diagnostic codes provide an historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.This 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.There are three configurations for the electrical wiring to the fuel metering valve. Verify your engine's configuration before you use this procedure.
Illustration 1 g01079998
Schematic for the electrical power supply
Test Step 1. Inspect the Electrical Connectors and Wiring
Illustration 2 g01073505
Terminal box
(1) J1/P1 connectors for the ECM
(2) J16/P16 connectors for the harness to the fuel metering valve
(3) J23 connector for the service tool
(4) 16 amp circuit breaker
(5) 6 amp circuit breaker
(6) J5/P5 connectors for the harness to the ITSM
(7) J9/P9 connector for the wiring to the customer's connections
Set the engine control to the OFF/RESET mode. Switch 16 amp circuit breaker (4) to the OFF position. Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".
Disconnect the J1/P1 connectors. Inspect the J1 connector and the P1 connector for damage, for corrosion, and for moisture. Reconnect the J1/P1 connectors.
Thoroughly inspect the following connections:
Electrical connections to each of the circuit breakers
Connectors for the 24 VDC power supply
Connections for the engine