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| Illustration 1 | g06172229 |
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Schematic for Engine Starting System | |
The ECM activates the start relay when the key start switch is in the START position and the direction switch is in the NEUTRAL position. If CID 168 is present, the diagnostic code must be corrected before performing the following procedure "Check the key start switch". See Troubleshooting, "Diagnostic Code List".
After the ECM detects the system voltage from the START input, the ECM will activate the starter relay. All the following conditions need to be true for the software to energize the start relay:
- Ignition Key in Start Position.
- The transmission in NEUTRAL position.
- Battery voltage is between 18 VDC and 32 VDC before the Start Relay is energized.
- Battery voltage is less than 32 VDC when the Start Relay is energized.
- Engine Speed is less than 400 RPM.
The starter relay has system battery voltage on one side of the relay contacts. When the starter relay is energized, system battery voltage is directed through the closed relay contacts. Next, the starter solenoids for the starter will energize. The starter solenoid contacts will close and +battery voltage will be applied to the starter to crank the engine for starting.
Perform the following procedure if the engine will not crank with the key start switch in the START position.
Note: Refer to the engine service manual for your machine if the engine cranks but the engine is not starting.
Verify that there are no active diagnostic codes for the intermediate starter relay. If a diagnostic code for the relay is active, troubleshoot the diagnostic code before attempting to start the engine.
Note: Poor harness connections are often the cause of a problem in electrical circuits. Before performing any troubleshooting procedure, inspect all the connectors involved in the circuit. Verify that all the connections in the circuit are dry, clean, secure, and in good condition. Each pin and socket in the connectors should mate correctly when the connectors are fastened together. Check for exposed wires at the connectors for nicks or abrasion. If a problem is found with any of the connections: correct the problem and verify that diagnostic code is still active, before performing the following procedures. For more information, refer to Troubleshooting, "Electrical Connector - Inspect".
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 1. Verify That The Machine Conditions Are Correct. A. Verify that the disconnect switch is in the ON position. B. Verify that the breaker for the starting system is not open. C. Verify that the parking brake is engaged. D. Verify that the transmission is in NEUTRAL. |
One or more of the listed machine conditions was NOT correct. |
YES - One or more of the listed machine conditions was not correct. Repair- Ensure that all the listed machine conditions are correct. Then attempt to start the engine again. STOP NO - All the listed machine conditions are correct. The engine will not crank and there are not any diagnostic codes for the intermediate starter relay. Proceed to Test Step 2. |
| 2. Check The Relays. A. The key start switch is in the OFF position. B. Obtain the aid of another technician. The other technician can place the key start switch in the START position. Observe the starter relays. The relays should create an audible "click" when the key start switch is first moved to the START position. |
The relays are being energized by the intermediate start relay. |
OK - The relays are being energized by the intermediate start relay. Proceed to Test Step 3. NOT OK - The relays are not being energized by the intermediate start relay. Repair: There is a problem in the circuit for the starter relay. Refer to the Troubleshooting section of this manual. Perform the diagnostic code procedure for the CID 444 diagnostic code to find the problem. The CID 444 indicates that the current is below normal or the circuit is open for the intermediate start relay. Find the problem in the relay circuit and repair the circuit. |
| 3. Check The Condition Of The Batteries A. The key start switch is in the OFF position. B. At the starter relays, measure the battery voltage from the contact that is connected to the red cable (109-RD(Red)) and a good frame ground. Verify that the correct voltage is present at the relay contact. If no voltage is present, check the circuit back to the batteries. Determine the reason for lack of system voltage at one side of the relay contacts. C. Verify that the battery connections are clean and tight. Perform Load test on the batteries. Use a 4C-4911 Battery Load Tester. Refer to Special Instruction, SEHS9249, "Use of 4C-4911 Battery Load Tester for 6, 8, and 12 V Lead Acid Batteries" and Special Instruction, SEHS7633, "Battery Test Procedure". |
The batteries pass the load test and the connections are in good condition. |
OK - The batteries and the connections are OK. Proceed to Test Step 4. NOT OK - The batteries do not pass the load test or the connections are not in good condition. Repair: Charge or replace the batteries. Clean the battery connections. Repair the battery connections. STOP |
| 4. Check The Voltage At The Starter A. Turn the key start switch to the OFF position. B. At the tractor starter motor, measure the system voltage between the +battery contact (cable RD(Red)) and a good frame ground. C. At the starter, fasten ONE clamp-on multimeter probe to the starter solenoid contact and fasten the other clamp-on probe to a good frame ground. D. Observe the multimeter for a voltage measurement while the key start switch is in the START position for a few seconds. |
System voltage is present at the + battery contacts (cable RD(Red)) on the starter. System voltage is present at the starter with the key start switch in the START position. |
OK - The system voltage is present at the starter solenoid contacts and system voltage is present at the contacts for the starter. Repair: The starters should be cranking the engine when the key start switch is in the START position. The starter has failed. Replace the starter. STOP NOT OK - There is a problem with the system voltage at the starter or at the solenoid for the starter. Repair: Investigate the circuit that is not providing the correct voltage at the starter or the solenoid for the starter. Repair the system voltage circuit. Verify the presence of voltage at the contact of the starter relay. If the voltage is not present at the solenoid for the starter with the key start switch in the START position. Check the operation of the relay. Check the wire from the starter relay to the solenoid of the starter. STOP |