SPRING 9T3867 - Caterpillar

Illustration 3 g01351255
Starter Relay location (View: right side of machine, under cover removed, looking up over the toolboxThe Machine Control ECM controls the engine cranking system for the machine. The ECM will initiate the engine cranking sequence based on the status of the Key Start Switch. When the Key Start Switch is in the ON position or in the START position, a system voltage input is supplied to the ECM through the key switch contacts. When the Machine Control ECM detects the system voltage at the START input, the ECM will activate the ON/OFF output for the Starter Motor Relay in order to initiate the engine cranking process provided the following machine conditions are present:
The engine speed is 0 rpm.
The system voltage is less than 36.0 VDC.
The left armrest is in the raised position.
The ECM internal "key override" function is not active.
There are no active diagnostic codes for the Armrest Position Switch or the Service Brake Pedal Limit Switch.The ECM key override function will disable the Starter Relay output when the engine speed is greater than 400 rpm. This protects against accidently engaging the Starter Motor when the engine is running.When the machine conditions are correct and the key switch is turned to the START position, the ECM will energize the Starter Relay. This will allow system voltage from the 60 amp Starter Relay Fuse to be directed to the Starter Motor Solenoid through the Starter Relay contacts.When the Starter Motor Solenoid is energized, +battery voltage directly from the batteries is connected to the starter motor terminal. This results in the starter motor cranking the engine.The Limp Home Switch can be used to bypass the ECM control of the Start Relay. When the Limp Home Switch is in the ON position and the Key Start Switch is in the START position, system voltage will be directed through the switch contacts in order to energize the Starter Relay. The ECM will monitor the status of the Limp Home Switch with a switch to ground input circuit.When the circuit is grounded, the ECM will determine that the Limp Home switch is in the ON position.Note: If the engine is cranking when the key start switch is in the START position and the engine is not starting, refer to the engine service manual for your model machine.In the event that the engine will not crank when the key start switch is in the START position, perform the following procedure.Verify that there are no active CID 0444 diagnostic codes for the Starter Motor Relay. If a diagnostic code for the relay is active, troubleshoot and repair the relay circuit problem before attempting to start the engine.Test Step 1. Verify That The Machine Conditions Are Correct
Verify that the following conditions are correct:
The disconnect switch is in the ON position.
The Starter Relay Fuse is not open.
The left armrest is in the raised position.
The ECM internal "key override" function is not active.Expected Result:One or