SWITCH ASSEM. (diff. press.) 7J2991 - Caterpillar

System Operation Description:The engine control has the ability to crank the engine when the engine control is placed in the RUN mode or the engine control is placed in the AUTO mode. When the engine control begins a cranking sequence, the Electronic Control Module (ECM) will activate the prelube system. Refer to the diagnostic functional test Troubleshooting, "Prelubrication System". The engine control will start the first crank cycle, when the prelube is completed. The crank cycle continues for the programmed time or the engine speed reaches the crank terminate speed. If crank terminate speed is not reached before reaching the cycle crank time, the starting motor will deactivate for a time that is equal to the cycle crank time.This process will repeat for a programmed amount of times (Total Number of Crank Cycles). If the engine does not start, Caterpillar Electronic Technician (ET) will display "OVERCRANK". The engine control will be in an idle state. The crank cycle can be restarted by turning the engine control to the OFF/RESET or to the STOP mode and then turning the engine control to the START mode.Note: When the starting motor fails to engage the flywheel due to a butt engagement, that crank cycle will still be counted in the total number of crank cycles.
Illustration 1 g01190695
Typical schematic
Test Step 1. Check for Connector Damage
Turn the engine control to the OFF/RESET mode.
Turn the battery disconnect switch to the OFF position.
Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
Check the ECM connector (allen head screw) for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Check the customer connector (allen head screw) for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
Check the harness and the wiring for abrasion and for pinch points. Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiringare free of corrosion, of abrasion and of pinch points.Results:
OK - The connectors and wiring are OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring need repair.Repair: Repair the connectors or wiring and/or replace the connectors or wiring.STOPTest Step 2. Attempt to Start the Engine
Connect Cat ET to the service tool connector J60/P60.
Turn the battery disconnect switch to the ON position.
Turn the engine control to the STOP mode.
Observe the "startup mode" parameters on the Cat ET status screen.
Turn the engine control to the RUN or to the AUTO mode. Continue monitoring engine parameters as the engine cranks.
The crank cycle will continue for the time that is equal to the cycle crank time that has been programmed or the crank cycle will continue until the engine speed reaches the crank terminate speed.
Turn the engine control to the OFF/RESET mode.
Turn the battery disconnect switch to the