G3520B Industrial Engine Caterpillar

The Electronic Control Module (ECM) has four outputs in order to indicate the status of engine operation: "Run Relay", "Crank Terminate Relay", "Engine Control Alarm Status" and "Fault Relay". These outputs can be used to energize indicator lamps or the outputs can be used to interface with other controls.

The ECM opens an internal circuit in order to set an output to OFF. The ECM closes the circuit in order to set the output to ON. When the circuit is closed and the output is ON, the ECM allows a maximum current of 0.3 amperes to flow through the circuit to a ground that is inside the ECM.

If excessive current flows through the circuit, a diagnostic code is generated. A short circuit to the +Battery side will also activate a diagnostic code.

Note: These circuits do not sink enough current for illumination of standard incandescent lights. If a lamp is burned out, replace the lamp with the lamp that is specified in the engine's Parts Manual.

"Run Relay" - This output indicates that the engine is in the "Run" status. The engine will start soon or the engine is running. While this output is energized, a short circuit to a positive voltage source or excessive current through the circuit will cause a diagnostic code to become activated. The ECM cannot diagnose this output while the output is OFF.

"Crank Terminate Relay" - This output indicates that the engine rpm is greater than the programmed engine speed that is required for disengagement of the starting motor. While this output is energized, a short circuit to a positive voltage source or excessive current through the circuit will cause a diagnostic code to become activated. The ECM cannot diagnose this output while the output is OFF.

"Engine Control Alarm Status" - This is the alarm output. This output indicates that the ECM has detected an electrical problem or an abnormal operating condition. While this output is energized, a short circuit to a positive voltage source or excessive current through the circuit will cause a diagnostic code to become activated. The ECM cannot diagnose this output while the output is OFF.

"Fault Relay" - This is the shutdown output. This output indicates that a potentially damaging operating condition was detected by the ECM. The ECM has shut down the engine. While this output is energized, a short circuit to a positive voltage source or excessive current through the circuit will cause a diagnostic code to become activated. The ECM cannot diagnose this output while the output is OFF.

A "323-03 Shutdown Lamp short to +batt" or "324-03 Warning Lamp short to +batt" diagnostic code can only be generated if a shutdown condition or an alarm condition is active. Failure to correct these serious conditions can result in engine damage.

Use the Caterpillar Electronic Technician (ET) to determine the event code or the diagnostic code that corresponds to the 323-03 or 324-03 diagnostic code. Troubleshoot that event code or that diagnostic code before you troubleshoot the 323-03 or 324-03 diagnostic code. Refer to Troubleshooting, "Troubleshooting with an Event Code" or Troubleshooting, "Troubleshooting with a Diagnostic Code".

The most likely causes of a diagnostic code for a status indicator is a poor electrical connection or a problem in a wiring harness. The next likely cause is a problem with an indicator. The least likely cause is a problem with the ECM.

Logged diagnostic codes provide a historical record. Before you begin this procedure, use ET to print the logged codes to a file.

The troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.

Illustration 1	g01087801
Schematic for the status indicators

Test Step 1. Inspect the Electrical Connectors and Wiring

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Illustration 2	g01087790
Terminal box (1) J2/P2 connectors for the ECM (2) J5/P5 connectors for the customer's connections (3) J10/P10 connectors for the harness to the optional control panel

1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

Note: Some indicators may obtain the status of the engine via a data link. If all of the status indicators are not directly controlled by the ECM, do not proceed with this test.

2. Thoroughly inspect each of the following connectors:
   • J2/P2 connectors

   • J5/P5 connectors

   • J10/P10 connectors on the terminal box

   1. Check the torque of the allen head screw for the ECM connectors. The proper torque is 6 ± 1 N·m (55 ± 9 lb in).
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   Illustration 3	g00994617
   Harness side of the P2 connector (P2-28) Run Relay (P2-29) Crank Terminate Relay (P2-30) Fault Relay (P2-31) Engine Control Alarm Status

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   Illustration 4	g01087800
   Harness side of the P5 connector (P5-7) Crank Terminate Relay (P5-8) Engine Control Alarm Status (P5-9) Fault Relay (P5-19) Run Relay

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   Illustration 5	g01087799
   Harness side of the P10 connector (P10-C) Crank Terminate Relay (P10-H) Engine Control Alarm Status (P10-P) Fault Relay (P10-Z) Run Relay

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the status indicators.

   Note: These outputs do not provide enough current for illumination of standard incandescent lights. If a lamp is burned out, replace the lamp with the lamp that is specified in the engine's Parts Manual.

   3. Inspect the wiring and the receptacles for the status indicators.

   4. Check the harness and wiring for abrasion and for pinch points from the status indicators to the ECM.

Expected Result:

All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - The components are not in good condition and/or at least one connection is improper.

  Repair: Perform the necessary repairs and/or replace parts, if necessary.

  Stop.

Test Step 2. Check for Diagnostic Codes

1. Connect Cat ET to the service tool connector on the terminal box. Refer to Troubleshooting, "Electronic Service Tools".

2. Restore the electrical power to the engine.

3. Attempt to start the engine and observe the status indicators. Allow a minimum of 30 seconds for any diagnostic codes to activate. Use the "Active Diagnostic" screen on Cat ET to look for the codes that are listed in Table 1:
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   Table 1

   Diagnostic Codes and Descriptions with Corresponding ECM Outputs
   Code	Description	ECM Output
   323-03	Shutdown Lamp short to +batt	"Fault Relay"
   324-03	Warning Lamp short to +batt	"Engine Control Alarm Status"
   443-03	Crank Terminate Relay short to +batt	"Crank Terminate Relay"
   445-03	Run Relay short to +batt	"Run Relay"

Expected Result:

There are no active diagnostic codes. The "Engine On" indicator and the "Crank Terminate" indicator (if equipped) illuminated normally. The "Active Alarm" indicator and the "Engine Failure" indicator did not illuminate.

Results:

• Yes (Original 443-03 or 445-03 Diagnostic Code) - The original diagnostic code was "443-03 Crank Terminate Relay short to +batt" or "445-03 Run Relay short to +batt". When the engine was started, the "Run Relay" indicator and the "Crank Terminate Relay" indicator (if equipped) illuminated normally. The "Engine Control Alarm Status" indicator and the "Fault Relay" indicator did not illuminate. There are no active diagnostic codes.

  Repair: The outputs for the status indicators seem to be operating correctly at this time. The original diagnostic code was probably caused by a poor electrical connection.If there is an intermittent problem that is causing the codes to be logged, refer to Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Yes (Original 323-03 or 324-03 Diagnostic Code) - The original diagnostic code was "323-03 Shutdown Lamp short to +batt" or "324-03 Warning Lamp short to +batt". When the engine was started, the "Run Relay" indicator and the "Crank Terminate Relay" indicator (if equipped) illuminated normally. The "Engine Control Alarm Status" indicator and the "Fault Relay" indicator did not illuminate. There are no active diagnostic codes.

  Repair: The 323-03 and 324-03 diagnostic codes can only be activated when the corresponding indicator is activated. There may still be a problem with the output for the alarm indicator or with the shutdown indicator. The alarm and/or the shutdown must be activated.

  Allow the engine operation to continue. Proceed to Test Step 3.

• Not OK (Active 323-03 or 324-03 Diagnostic Code) - There is an active "323-03 Shutdown Lamp short to +batt" or "324-03 Warning Lamp short to +batt". There must be a shutdown condition before a 323-03 diagnostic code can be generated. There must be an alarm condition before a 324-03 diagnostic code can be generated. Both of these conditions are serious.

  Repair: Use Cat ET to determine the event code or the diagnostic code that corresponds to the 323-03 or 324-03 diagnostic code. Troubleshoot that event code or that diagnostic code before you troubleshoot the 323-03 or 324-03 diagnostic code. Refer to Troubleshooting, "Troubleshooting with an Event Code" or Troubleshooting, "Troubleshooting with a Diagnostic Code".Exit this procedure. After you have resolved the condition, return to this procedure in order to troubleshoot the 323-03 and/or 324-03 diagnostic code, if necessary.

  Stop.

• Not OK (Active 443-03 or 445-03 Diagnostic Code) - When the engine was started, the "Run Relay" indicator and/or the "Crank Terminate Relay" indicator (if equipped) did not illuminate normally. The "Engine Control Alarm Status" indicator and the "Fault Relay" indicator did not illuminate. A 443-03 or 445-03 diagnostic code was activated. There is a problem with the output for the "Run Relay" indicator and/or with the "Crank Terminate Relay" indicator (if equipped). Proceed to Test Step 4.

Test Step 3. Check for Proper Operation of the Status Indicators for the Alarm and Shutdown

Allow the engine operation to continue for this procedure.

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Illustration 6	g01072562
Front view (1) Unfiltered engine oil pressure sensor (2) Filtered engine oil pressure sensor (3) Connectors for the engine oil pressure sensors

1. During engine operation, disconnect connector (3) for unfiltered engine oil pressure sensor (1). Observe the "Engine Control Alarm Status" indicator on the control panel (if equipped).

   If you are only troubleshooting a "324-03 Warning Lamp short to +batt", proceed to the "Expected Result".

Note: When the filtered engine oil pressure sensor is disconnected, the engine will shut down.

2. Disconnect connector (3) for filtered engine oil pressure sensor (2). Observe the "Fault Relay" indicator on the control panel (if equipped).

3. Use the "Diagnostics" screen on Cat ET to look for active diagnostic codes.

Expected Result:

The "Engine Control Alarm Status" indicator illuminated and a "542-03 Unfiltered Engine Oil Pressure open/short to +batt" diagnostic code was activated when the unfiltered engine oil pressure sensor is disconnected.

The "Fault Relay" indicator illuminated and a "100-03 Engine Oil Pressure open/short to +batt" diagnostic code was activated when the filtered engine oil pressure sensor is disconnected. The engine was shut down.

Results:

• OK - The indicators, diagnostic codes, and shutdown were activated according to the "Expected Result". The outputs for the status indicators seem to be operating correctly at this time. The original problem seems to be resolved.

  Repair: The original diagnostic code was probably caused by a poor electrical connection.If there is an intermittent problem that is causing the codes to be logged, refer to Troubleshooting, "Inspecting Electrical Connectors".

  Stop.

• Not OK - The "Engine Control Alarm Status" indicator and/or the "Fault Relay" indicator did not illuminate normally when the sensors were disconnected. A "323-03 Shutdown Lamp short to +batt" and/or a "324-03 Warning Lamp short to +batt" diagnostic code was generated. There is a problem with the output for the status indicators. The "542-03" and the "100-03" diagnostic codes were generated. The engine was shut down. Reconnect the connectors and proceed to Test Step 4.

Test Step 4. Measure the Voltage for the Suspect Output at the P2 Connector

1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

2. Insert a 7X-1710 Multimeter Probe into the suspect control terminal in the P2 connector.

3. Connect the positive lead of a voltmeter to the end of the 7X-1710 Multimeter Probe. Connect the voltmeter's negative lead to the ground strap for the master ECM.

4. Restore the electrical power to the engine. Set the engine control to the STOP mode.

5. Note the voltage that is displayed on the voltmeter.

6. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

7. Disconnect the wire from the suspect indicator. Be sure to disconnect the wire that comes from the ECM.

8. Insulate the end of the wire with electrical tape in order to ensure that the wire does not create a short circuit.

9. Restore the electrical power to the engine. Set the engine control to the STOP mode.

10. Note the voltage that is displayed on the voltmeter.

Expected Result:

Before the suspect indicator was disconnected, voltage was displayed on the voltmeter. After the suspect indicator was disconnected, the voltmeter displayed approximately zero volts.

Results:

• Yes - Before the suspect indicator was disconnected, voltage was displayed on the voltmeter. After the suspect indicator was disconnected, the voltmeter displayed approximately zero volts. There is a problem in the customer's equipment.

  Repair: The problem could be caused by a poor electrical connection, by a wire, or by a component in the customer's equipment.Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.Thoroughly inspect all wiring and all connectors in the customer's equipment. Refer to Troubleshooting, "Inspecting Electrical Connectors".If you suspect that the indicator has an internal short circuit, temporarily install a known good indicator for the suspect indicator. Test the indicator. Verify that the problem is resolved.Make the necessary repairs, when possible. Replace parts, if necessary.

  Stop.

• No - Before the suspect indicator was disconnected, voltage was displayed on the voltmeter. After the suspect indicator was disconnected, the voltage was still displayed on the voltmeter. Proceed to Test Step 5.

Test Step 5. Check the Wiring for the Status Indicator

1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

2. Use a 151-6320 Wire Removal Tool to remove the suspect terminal from the P2 connector.

3. Insulate the wire's terminal with electrical tape in order to ensure that the terminal does not create a short circuit.

4. Fabricate a jumper wire with Deutsch terminals on the ends. Insert one end of the jumper wire into the open terminal of the P2 connector.

5. Connect a voltmeter lead to the end of the jumper wire that is not inserted into the connector.

6. Connect the other lead of the voltmeter to the ground strap for the ECM.

7. Restore the electrical power to the engine. Set the engine control to the STOP mode. Observe the reading on the voltmeter.

Expected Result:

The voltage is approximately zero.

Results:

• OK - The voltage is approximately zero. After the wire for the status indicator was removed from the P2 connector, the reading on the voltmeter was approximately zero. There is a problem in the wiring between the P2 connector and the status indicator.

  Repair: Repair the connection and/or the wiring, when possible. Replace parts, if necessary.

  Stop.

• Not OK - The voltage remained. After the wire for the status indicator was removed from the P2 connector, voltage was still displayed on the voltmeter. There may be a problem with the master ECM.

  Repair: It is unlikely that the master ECM has failed. Exit this procedure and perform this procedure again. If the problem is not resolved, perform the following steps:Temporarily install a new master ECM. Refer to Troubleshooting, "Replacing the ECM".If the problem is resolved with the new ECM, install the original ECM and verify that the problem returns. If the new ECM operates correctly and the original ECM does not operate correctly, replace the original ECM. Refer to Troubleshooting, "Replacing the ECM".

  Stop.