TUBE AS 7W6751 - Caterpillar

Illustration 1 g01071938
Keyswitch input to the ECMBattery power is provided to the ECM input for the keyswitch circuit when the keyswitch is in the ON position. This input must be powered in order for the ECM to control the engine operating functions.
Illustration 2 g01071934
Schematic
Illustration 3 g01071935
Terminal locations at the ECMTest Step 1. Inspect the Electrical Connectors and the Wiring
Thoroughly inspect J1/P1 ECM connector, the battery connections and the connections to the keyswitch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the following connections:
J1/P1-4 (Unswitched +Battery)
J1/P1-5 (-Battery)
J1/P1-6 (Ignition keyswitched +Battery)
Check the allen head screws for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque value.
Check the harness and wiring for abrasion and for pinch points from the battery to the ECM, and from the keyswitch to the ECM.Expected Result:All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring should be free of corrosion, of abrasion or of pinch points.Results:
OK, Troubleshooting a 168-2 Code - Proceed to Test Step 2.
Not OK - There is a problem with the connectors or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.STOPTest Step 2. Check the Battery Voltage at the ECM
Insert a 40-pin breakout T between the J1 and P1 ECM connector.
Turn the keyswitch to the ON position . The engine must be OFF.
Measure the voltage between P1-6 (ignition keyswitched +Battery) and P1-5 (-Battery).
Toggle the keyswitch between the OFF position and the ON position. The engine must be OFF.
Measure the voltage between P1-4 (unswitched +Battery) and P1-5 (-Battery).Expected Result:For 12 Volt Systems, the measured voltage is a constant 11.0 to 13.5 VDC with no suspected intermittent problems at this time. For 24 Volt systems, the measured