| Diagnostic Codes Table | |||
|---|---|---|---|
| J1939 Code | CDL Code | Code Description | System Response |
| 677-5 | 444-5 | Engine Starter Motor Relay : Current Below Normal | The Electronic Control Module (ECM) detects an open circuit and/or a short to the +Battery in the start relay. The ECM can only detect this condition when the start relay is not energized.
The code is logged. |
| 677-5 | 444-6 | Engine Starter Motor Relay : Current Above Normal | The ECM detects a short circuit to ground in the start relay. The ECM can only detect this condition when the start relay is energized.
The code is logged. |
The ECM can crank the engine when the Engine Control Switch (ECS) is placed in the START position. After the ECS is placed in the START position, the ECM will begin the prelube cycle. When the prelubrication pressure switch opens, the ECM will start the first crank cycle. 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. If crank terminate speed is not reached before the crank cycle time, the starting motor will deactivate at the end of the crank cycle 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 process can be restarted by turning the ECS to the OFF position. Next turn the ECS to the STOP position. Then turn the ECS to the START position.
The ECM will send a signal to the starting motor relays after the prelube cycle is complete. The starting motor relays will energize closing the normally open contacts of the relays. Current will flow to the starting motors from the "mag relay breaker". The starting motors will begin to crank the engine.
The engine can be manually started by using the manual crank switch.
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| Illustration 1 | g03658526 |
There are also configuration parameters that are used to configure the ECM for the type and the location of the starting motors. The following types of starting motors can be used on this engine:
- Air starting motor
- Electric starting motor
The wiring for each of these types of engine starting circuits is similar. Follow this procedure in order to troubleshoot the circuit diagnostics for any of these types of engine starting system.
The ECM can control a secondary starting system that is installed on the engine opposite the primary starting system. Refer to Troubleshooting, "Configuration Parameters" for information that is related to the configuration parameters that are for the secondary starting system.
ECM Activation of the Starting Motors
The ECM utilizes two output drivers in order to crank the engine. Each output driver is provided with 24 VDC during engine cranking. The circuits for the output drivers utilize a return line to the ECM. This circuit includes crank relays that can be powered by an external power supply in order to override the ECM activation of the starting motors.
Manual Overrides for the Engine Starting System
The engine can be manually cranked by using a manual crank switch that can be wired into the engine interface connector. The engine starting circuit incorporates four crank relays. When the relay coils are powered by 24 VDC, the starting motor magnetic switches are fused at the low current power distribution panel. The switch and the wiring for the circuit must be supplied by the customer.
Caterpillar Electronic Technician (ET) can be used in order to override the output command that is provided by the engine state control. This override can be used to diagnose the circuit that is for the starting motor magnetic switches. View the "Starting System Relay Status" that is available in Cat ET in order to determine the status of the ECM outputs.
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
1. Inspect the Electrical Connectors and the Wiring A. Turn the main disconnect switch to the OFF position. B. Thoroughly inspect the connectors that are associated with the starting system. Ensure that a circuit breaker has not tripped. Refer to Troubleshooting, "Electrical Connectors - Inspect " for details. C. Perform a D. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect " for the correct torque values. E. Check the harness and the wiring for abrasion and for pinch points. |
Connectors |
Results: The connectors and wiring are OK. Proceed to Test Step 2 Results: The connectors and/or wiring need repair. Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the problem. |
2. Check for Active Diagnostic Codes A. Connect Cat ET to the service tool connector. B. Restore the electrical power to the ECM. C. Select diagnostic tests from Cat ET. D. Select the "Override Parameters" screen on Cat ET. E. Activate the override for the appropriate starting system for your application. F. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes for the starting system. Note: Wait at least 30 seconds in order for the diagnostic code to become active. G. Deactivate the override for the starting system. H. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. I. Turn the main disconnect switch to the OFF position. |
Active Diagnostic Codes |
Results: No diagnostic codes are active, but a problem is suspected in the circuit for the starting system. Repair: The circuit for the starting system appears to be operating correctly between the ECM and the starting motor magnetic switch. Isolate the starting motor magnetic switch from the primary circuit and the secondary circuit. Test the operation of the switch. If a problem with the switch is discovered, replace the switch. If the switch is OK, there is a problem in the circuit to the starting motors. There may be a problem in the power cables from the batteries to the starting motors. Check each of the circuits for problems. Check the operation of the starting motors. Perform the necessary repairs. Verify that the repair eliminates the problem. Results: A -6 diagnostic code is active at this time. Proceed to Test Step 3 Results: A -5 diagnostic code is active at this time. Proceed to Test Step 4 |
3. Create an Open Circuit at the Connector for the Crank Relay A. Turn the ECS to the STOP position. B. Disconnect the wires from terminal 3 and terminal 4 on the start relays. Ensure that the wires are isolated from engine ground and from sources of electrical power. C. Turn the ECS to the STOP position. D. Monitor the active diagnostic screen on Cat ET. Check for a -5 diagnostic code for the start relay. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. E. Proceed to the "Diagnostic Overrides" screen on Cat ET. Activate the override for the starting system. F. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic code to become active. G. Turn the ECS to the OFF position. |
Open Circuit |
Results: A -5 diagnostic code became active after disconnecting the crank relay at the connector. The wires from the ECM to the start relays are OK. Repair: The problem may be in one of the coils of the start relays. Install new start relays. Clear any logged diagnostic codes. Results: A -6 diagnostic code remains active. There is a short between the connector for the relay and the ECM. There may be a problem with the ECM. Proceed to Test Step 4 |
4. Create a Short at the Connector for the Crank Relay A. Turn the ECS to the STOP position. B. Install a jumper wire between terminal 4 and terminal 3 at the start relay. C. Turn the ECS to the STOP position. D. Monitor the active diagnostic code screen on Cat ET. Check for a -5 diagnostic code for the start relay. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. E. Select the "Override Parameters" screen on Cat ET. F. Activate the override for the starting system. G. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic code to become active. I. Deactivate the override for the starting system. J. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. K. Turn the ECS to the OFF position. |
Crank Relay |
Results: A -6 diagnostic code is active when the jumper is installed. The wires from the ECM to the start relay are OK. Repair: Temporarily replace each of the relays. Check if replacement of the relays has corrected the original problem. If the problem has not been resolved, there is a problem in the harness between the relay and the starting motor magnetic switch. Repair the harness or replace the harness. Verify that the repair eliminates the problem. Results: The -5 diagnostic code remains active with the jumper in place. There is an open circuit between the ECM and the connector for the crank relay. There may be a problem with the ECM. Proceed to Test Step 5 |
5. Check the Operation of the ECM by Creating an Open at the ECM Connector: A. Disconnect the J2/P2 ECM connector. B. Remove the wires for the starting system from the ECM connector. C. Fabricate two jumper wires that are long enough to create a test circuit across the ECM connector. Crimp connector sockets to each end of the jumper wire. D. Install a wire jumper into each of these terminal locations. Ensure that the wire jumpers do not come in contact with any other wire in the harness or in contact with engine ground. E. Reconnect the ECM connector. F. Restore the electrical power to the ECM. G. Select diagnostic tests from Cat ET. H. Select the "Override Parameters" screen on Cat ET. I. Activate the override for the appropriate starting system. J. Monitor the active diagnostic code screen on Cat ET. Note: Wait at least 30 seconds in order for the diagnostic code to become active. K. Deactivate the override. L. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. M. Turn the main disconnect switch to the OFF position. |
Open |
Results: The ECM is operating properly. The problem is in the wiring between the ECM and the connector for the crank relay. Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the problem. Results: One of the following conditions exists: The -5 diagnostic code is not active when the wire jumpers are open. The -6 diagnostic code is not active when the wire jumpers are shorted together. Repair: There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance. |
6. Check the Operation of the ECM by Creating a Short Circuit at the ECM Connector. A. Connect the loose ends of the jumper wires. B. Restore the electrical power to the ECM. C. Select diagnostic tests from Cat ET. D. Select the "Override Parameters" screen on Cat ET. E. Activate the override for the appropriate starting system. F. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic code to become active. G. Deactivate the override. H. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active. I. Turn the main disconnect switch to the OFF position. J. Restore the wiring to the original configuration. |
Short |
Results: The ECM is operating properly. The problem is in the wiring between the ECM and the connector for the crank relay. Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the problem. Results: One of the following conditions exists: The -5 diagnostic code is not active when the wire jumpers are open. The -6 diagnostic code is not active when the wire jumpers are shorted together. Repair: There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, "Test ECM Mode". Note: Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN) for assistance. |
7. Check the Voltage to the Normally Open Contacts of the Start Relay A. Turn the ECS to the STOP position B. Remove the wire from terminal 1 of the start relays. Measure the voltage between the wire and the engine ground. C. Restore the wiring to the original configuration. |
24 ± 3 V |
Results: The voltage measurement is 24 ± 3 V. Proceed to Test Step 8. Results: The voltage measurement is not 24 ± 3 V. Repair: The problem appears to be in the wiring between the +Battery and the start relay. Verify that any breakers between the start relays and the +Battery terminal are not tripped. STOP |
8. Check the Voltage from the Start Relay to the Starting Motors A.Turn the ECS to the STOP position. B. Remove the wires from terminal 2 at the start relays. C. Proceed to the "Diagnostic Overrides" screen on Cat ET. Activate the override for the starting system. D. Measure the voltage between terminal 2 of the start relays and the engine ground. E. Turn the ECS to the STOP position F. Restore the wiring to the original configuration. |
24 ± 3 V |
Results: The voltage measures 24 ± 3 V. Proceed to Test Step 9. Results: The voltage does not measure 24 ± 3 V. Repair: Voltage is present at the normally open contacts of the start relays. There are no diagnostic codes for the start relays. Voltage is not present at the starting motors. Replace the start relays. Verify that the repair eliminated the problem. |
9. Check the Voltage at the Starting Motors A. Turn the ECS to the STOP position. B. Remove the wires from the starting motor solenoids. C. Proceed to the "Diagnostic Overrides" screen on Cat ET. Activate the override for the starting system. D. Measure the voltage between the wires at the starting motor solenoid and engine ground. E. Restore the wiring to the original configuration. |
24 ± 3 V |
Results: The voltage measures 24 ± 3 V. The problem appears to be in the starting motor solenoid. Repair: Verify the continuity of the return wire for the starting motor solenoid between terminal G and the -Battery. If the wire for the starting motor solenoid is OK, verify that you have continuity on the +Battery wire for the solenoid between terminal +Batt and terminal +Battery. If the wires to the solenoid are OK, replace the starting motor solenoid. Results: The voltage does not measure 24 ± 3 V. The problem is in the wiring between the start relay and the starting motor solenoid. Repair: Repair the wiring. STOP |
If the procedure did not correct the issue, contact your Cat Dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).