C175-16 Locomotive Engine Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the engine starting system. Also, use this procedure if one of the diagnostic codes in Table 1 is active or easily repeated.

Table 1

Diagnostic Codes Table
Description	Conditions which Generate this Code	System Response
2727-5 Starting System #1 Relay : Current Below Normal	The Electronic Control Module (ECM) detects an open in the circuit for the starter relay. The ECM detects a short to battery voltage in the circuit for the starter relay. The ECM can only detect this condition when the output driver is not activated.	The code is logged.
2727-6 Starting System #1 Relay : Current Above Normal	The ECM detects a short in the circuit for the starter relay. The ECM can only detect this condition when the output driver is activated.
2728-5 Starting System #2 Relay : Current Below Normal	The Electronic Control Module (ECM) detects an open in the circuit for the starter relay. The ECM detects a short to battery voltage in the circuit for the starter relay. The ECM can only detect this condition when the output driver is not activated.	The code is logged.
2728-6 Starting System #2 Relay : Current Above Normal	The ECM detects a short in the circuit for the starter relay. The ECM can only detect this condition when the output driver is activated.

Use this procedure to troubleshoot the electrical system if a problem is suspected with the starting system.

The ECM is provided with the ability to begin the engine cranking at any time after the ECM has received keyswitch power. The ECM receives the start command from the EMCP 3 via the global CAN data link. Once this request is received, the engine is placed into the "Prestart State" of the control for the engine state. If the engine is equipped with a prelubrication system, the engine will wait until the prelube cycle has been completed before initiating engine cranking.

Configuration Parameters

The settings of the following configuration parameters control engine starting:

• Starting System #1 Maximum Number of Crank Cycles

• Starting System #1 Crank Cycle Rest Interval

• Starting System #1 Crank Duration

• Crank Terminate RPM

Configuration parameters for Starting System #2 are also available. Refer to Troubleshooting, "Configuration Parameters" for information that is related to these parameters.

Illustration 1	g06091129
Schematic for the engine starting system

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

• Hydraulic 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.

Illustration 2	g03321063
Location of the control box connectors for the engine starting system (1) Right rail connector (2) J2/P2 ECM connector (3) Engine interface connector (4) Left rail connector (5) Manual crank relay (RH) (6) Manual crank relay (LF)

Illustration 3	g01560016
Terminal locations at the P2 ECM connector for the engine starting system (P2-32) Right starter enable − (P2-44) Right starter enable + (P2-59) Left starter enable + (P2-60) Left starter enable −

Illustration 4	g01533453
Terminal locations at the keyswitch relay and the relay for the power mode circuit (Terminal 1) Power to the starting motor magnetic switch (Terminal 2) Power from the override switch that is used to override the ECM signal (Terminal 3) Signal line or return line from the ECM (Terminal 4) Power or return for the secondary circuit of the relay that is for the manual override (Terminal 5) Return for the control circuit of the relay

Illustration 5	g01155187
Terminal locations at the connector for the starting motor magnetic switch (Terminal 1) Relay signal circuit to the pump (Terminal 2) Return

Table 2

Troubleshooting Test Steps	Values	Results
1. Inspect the Electrical Connectors and the Wiring A. Turn the battery 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 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit. 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.
2. Attempt to Start the Engine A. Turn the battery disconnect switch to the ON position. B. At the control panel, send a start command to the engine. C. Check the engine state parameter on the EMCP in order to ensure that the engine state control is commanding the engine to crank. Note: The engine state must cycle through the "PRE-START" state prior to cranking the engine. The engine prelubrication must successfully be completed before the engine is allowed to exit "PRE-START". The crank cycle will continue for a time that is equal to the crank duration that has been programmed. The crank cycle may continue only until the engine speed exceeds the crank terminate speed. D. Turn the battery disconnect switch to the OFF position.	Start - Up Engine	Results: The engine state parameter on the EMCP displays "CRANKING". The engine cranks. Repair: The engine starting system appears to be operating correctly. If an intermittent problem with the starting system is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent electrical problems. If you are troubleshooting a problem with the manual override control for the starting system, proceed to Test Step 3 Results: The status for the engine state parameter displays "CRANKING". The engine does not crank. Ensure that the circuit breaker for the engine starting system and the main circuit breaker have not been tripped. If the circuit breakers are OK, proceed to Test Step 5
3. Check the Signal for the Manual Override at the Engine Interface Connector A. Turn the battery disconnect switch to the ON position. B. At the engine interface connector, use a wire removal tool to remove the appropriate wire that is for the appropriate override switch. a. For starters on the left side of the engine, remove the wire from terminal location 26 from the engine interface connector. b. For starters on the right side of the engine, remove the wire from terminal location 27 ) from the engine interface connector. C. With the override switch in the ON position, use a multimeter to check the voltage at the loose end of the wire. D. Turn the battery disconnect switch to the OFF position.	24 ± 3 VDC	Results: The voltage is 24 ± 3 VDC. The wiring that has been installed by the customer is OK. Proceed to Test Step 4 Results: The voltage is not 24 ± 3 VDC. Repair: There is a problem in the switch wiring that has been installed by the customer. Trace the wiring to the switch and ensure that there is power to the switch. Check for proper operation of the switch. Perform the necessary repairs. Verify that the original problem has been resolved.
4. Check the Power for the Override Circuit at the Crank Relay A. At the control box, remove the relays for the suspect starting circuit. a. Perform this procedure for the starting motors on the left side of the engine: 1. Remove the crank relay (No. 3) for the power circuit to the starting motor magnetic switch. 2. Remove the crank relay (No. 4) for the return circuit to the starting motor magnetic switch. b. Perform this procedure for the starting motors that are on the right side of the engine: 1. Remove the crank relay (No. 1) that is for the power circuit to the starting motor magnetic switch. 2. Remove the crank relay (No. 2) that is for the return circuit to the starting motor magnetic switch. B. Turn the battery disconnect switch to the ON position. Place the override switch in the ON position. C. Use a multimeter to check the voltage between terminal 4 at the power circuit relay and terminal 4 (return). D. Turn the battery disconnect switch to the OFF position. Place the override switch in the OFF position. Restore the wiring to the original configuration.	24 ± 3 VDC	Results: The voltage is 24 ± 3 VDC. Repair: The wiring for the circuit in the crossover harness is OK. There may be a problem with the primary coil for one of the relays. Replace the relay for the power circuit to the starting motor magnetic switch. Retest the system in order to validate the repair. If the repair did not resolve the problem, replace the relay for the return circuit to the starting motor magnetic switch. Verify that the repair resolved the original problem. Results: The voltage is not 24 ± 3 VDC. Repair: Check that the fuse for the circuit is not blown. If the fuse is in good repair, the problem is in the crossover harness in the control box. Repair the harness or replace the harness. Verify that the original problem has been resolved. If the problem is not resolved, proceed to the next step.
5. Check for Active Diagnostic Codes A. Connect Cat ET to the service tool connector. B. Turn the battery disconnect switch to the ON position. 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 battery 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 original problem has been resolved. Results: A -6 diagnostic code is active at this time. Proceed to Test Step 7 Results: A -5 diagnostic code is active at this time. Proceed to Test Step 9
6. Create an Open at the Connector for the Starting Motor Magnetic Switch A. Disconnect the connector from the starting motor magnetic switch for the appropriate starting system. B. Turn the battery disconnect switch to the ON position. C. Select diagnostic tests from Cat ET. D. Select the "Override Parameters" screen on Cat ET. E. 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. 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 battery disconnect switch to the OFF position.	Active Diagnostic Codes	Results: A -5 diagnostic code became active after disconnecting the connector for the starting motor magnetic switch. Repair: Temporarily install a new starting motor magnetic switch. Verify that there are no active diagnostic codes for the starting system. Clear any logged diagnostic codes. Results: A -6 diagnostic code remains active. There is a short between the connector for the starting motor magnetic switch and the ECM. There may be a problem in the circuit between the crank relay and the switch. Proceed to Test Step 7
7. Create an Open Circuit at the Connector for the Crank Relay A. Disconnect the relay connector for the power circuit that is for the appropriate starting system. Refer to Illustration 1 for the schematic of the circuit. B. Turn the battery disconnect switch to the ON position. 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 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 battery disconnect switch to the OFF position.	Open Circuit	Results: A -5 diagnostic code became active after disconnecting the crank relay at the connector. Repair: Temporarily install a new relay. Check for active diagnostic codes. If the -6 diagnostic code remains active after replacing the relay, there is a short in the harness. Check the harness from the relay to the starting motor magnetic switch. Repair the harness or replace the harness. Clear any logged diagnostic codes. Verify that the original problem has been resolved. 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 10
8. Create a Short at the Connector for the Starting Motor Magnetic Switch A. Disconnect the connector for the starting motor magnetic switch. Install a jumper wire between the terminals at the connector for the switch. Refer to Illustration 1 for the schematic of the circuit. B. Turn the battery disconnect switch to the ON position. C. Select diagnostic tests from Cat ET. D. Select the "Override Parameters" screen on Cat ET. E. 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.	Short	Results: A -6 diagnostic code is active when the jumper wire is installed. Repair: There is a problem with the starting motor magnetic switch. Temporarily install a new switch. Verify that there are no active diagnostic codes for the starting system. Clear any logged diagnostic codes. Results: The -5 diagnostic code remains active with the jumper in place. Verify that the wire at terminal 2 of the connector for the switch has continuity to the −Battery. If the return circuit is OK, the open circuit is between the ECM and the connector for the starting motor magnetic switch. Proceed to Test Step 9
9. Create a Short at the Connector for the Crank Relay A. Disconnect the relay for the power circuit and the relay for the return circuit from the connectors at the control box. Refer to Illustration 1 for the schematic of the circuit. B. Fabricate a jumper wire that is long enough to create a test circuit between the two relay connectors. Crimp spade terminals to each end of each of the jumper wire. C. Install one end of the jumper wire into terminal 3 at each of the relay connectors. D. Turn the battery disconnect switch to the ON position. E. Select diagnostic tests from Cat ET. F. Select the "Override Parameters" screen on Cat ET. G. Activate 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 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 battery disconnect switch to the OFF position.	Crank Relay	Results: The engine harness and the ECM 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 has resolved the original 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 10
10. 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 appropriate starting system from the output driver and the return circuit at the ECM connector. Refer to Illustration 1 for the schematic of the circuit. 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. Turn the battery disconnect switch to the ON position. 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 70 seconds in order for the diagnostic codes to become active. M. Remove electrical power from the engine.	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. 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. Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit in order to ensure that the original problem has been resolved. If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.
11. 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. Turn the battery disconnect switch to the ON position. 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 70 seconds in order for the diagnostic codes to become active. I. Turn the battery 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. 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. Perform the following procedure: 1. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". 2. Recheck the circuit in order to ensure that the original problem has been resolved. If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved. If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.

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).