G3500 A3 Engines Caterpillar

Use this procedure to troubleshoot the following diagnostic codes:

• 323-3 Engine Shutdown Lamp voltage above normal

• 324-3 Warning Lamp (Action) voltage above normal

• 444-3 Starter Motor Relay voltage above normal

• 445-3 Run Relay voltage above normal

The Electronic Control Module (ECM) has the following four outputs that are used to indicate the status of engine operation:

• Engine control alarm status

• Run relay

• Crank terminate relay

• 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 turn off an output. The ECM closes the circuit in order to turn on an output. When the circuit is closed and the output is turned 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.

"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.

"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.

A 323-3 or 324-3 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.

Determine the event code or the diagnostic code that corresponds to the 323-3 or 324-3 diagnostic code. Troubleshoot that event code or that diagnostic code before you troubleshoot the 323-3 or 324-3 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.

Note: The Advisor monitor display obtains the status of the engine via a data link. Do not use this test to troubleshoot problems with the status indicators on the Advisor monitor display.

The troubleshooting procedure may generate additional diagnostic codes. Correct the cause of the original diagnostic code first. Clear the diagnostic codes after the problem is resolved.

Illustration 1	g01251044
Schematic for the status indicators

Test Step 1. Inspect the Electrical Connectors and Wiring

1. Set the engine control to the OFF/RESET position.

   Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".

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   Illustration 2	g01392084
   Location of the ECM connectors for the status indicators (typical left side front engine view) (1) J2/P2 ECM connectors

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   Illustration 3	g01393423
   Location of the connectors for the status indicators (typical left side rear engine view) (2) Interface box (3) Engine interface connector (40 pin)

2. Thoroughly inspect ECM connectors (1). Also, thoroughly inspect engine interface connector (3) that is mounted on interface box (2).

   1. Check the allen head screw for each of the ECM connectors for the proper torque.
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      Illustration 4	g01393570
      Terminal locations at the J2/P2 ECM connectors that are for the status indicators (P2-28) Run relay (P2-29) Crank Terminate Relay (P2-30) Fault relay (P2-31) Engine control alarm status

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      Illustration 5	g01393448
      Terminal locations at the engine interface connector that are for the status indicators (Terminal 20) Engine control alarm status (Terminal 25) Fault relay (Terminal 27) Crank Terminate Relay (Terminal 29) 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.

   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. Establish communication between Caterpillar Electronic Technician (ET) and the engine ECM. Refer to Troubleshooting, "Electronic Service Tools", if necessary.

2. Attempt to start the engine and observe the status indicators. Allow a minimum of 30 seconds for any diagnostic codes to activate. Check 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
   323-3	Engine Shutdown Lamp voltage above normal	"Fault Relay"
   324-3	Warning Lamp (Action) voltage above normal	"Engine Control Alarm Status"
   443-3	Starter Motor Relay voltage above normal	"Crank Terminate Relay"
   445-3	Run Relay voltage above normal	"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:

• OK (Original 443-3 or 445-3 Diagnostic Code) - The original diagnostic code was a 443-3 or 445-3. When the engine was started, the "Run Relay" indicator and the "Crank Terminate" 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

• OK (Original 323-3 or 324-3 Diagnostic Code) - The original diagnostic code was a 323-3 or 324-3 diagnostic code. When the engine was started, the "Run Relay" indicator and the "Crank Terminate" 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 323-3 and 324-3 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 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 323-3 or 324-3 Diagnostic Code) - There is an active 323-3 or 324-3 diagnostic code. There must be a shutdown condition before a 323-3 diagnostic code can be generated. There must be an alarm condition before a 324-3 diagnostic code can be generated. Both of these conditions are serious.

  Repair: Determine the event code or the diagnostic code that corresponds to the 323-3 or 324-3 diagnostic code. Troubleshoot that event code or that diagnostic code before you troubleshoot the 323-3 or 324-3 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 323-3 and/or 324-3 diagnostic code, if necessary.

  STOP

• Not OK (Active 443-3 or 445-3 Diagnostic Code) - When the engine was started, the "Run Relay" indicator and/or the "Crank Terminate" indicator (if equipped) did not illuminate normally. The "Engine Control Alarm Status" indicator and the "Fault Relay" indicator did not illuminate. A 443-3 or 445-3 diagnostic code was activated. There is a problem with the output for the "Run Relay" indicator and/or the "Starter motor 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 to remain running for this procedure.

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Illustration 6	g01395922
Top view of the front of the engine (4) Unfiltered engine oil pressure sensor (5) Filtered engine oil pressure sensor

1. During engine operation, disconnect the connector for unfiltered engine oil pressure sensor (1). Observe the "Engine Control Alarm Status" indicator.

   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 the connector for filtered engine oil pressure sensor (2). Observe the "Fault Relay" indicator.

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 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 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 diagnostic code and/or a 324-03 diagnostic code was generated. There is a problem with the output for the status indicators. The 542-03 diagnostic code and the 100-03 diagnostic codes were generated. The engine was shut down. Connect the connectors and proceed to Test Step 4.

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

1. Set the engine control to the OFF/RESET position.

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.

4. Set the engine control to the COOLDOWN/STOP position.

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

6. Set the engine control to the OFF/RESET position.

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. Set the engine control to the COOLDOWN/STOP position.

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:

• OK - 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, a wire, or a component in the customer's equipment.

  Set the engine control to the OFF/RESET position.

  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

• Not OK - 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 position.

2. Remove the suspect terminal from the P2 ECM 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 socket terminals on the ends. Insert one end of the jumper wire into the open terminal of the P1 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. Set the engine control to the COOLDOWN/STOP position. 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 ECM connector, the reading on the voltmeter was approximately zero. There is a problem in the wiring between the P2 ECM 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 ECM connector, voltage was still displayed on the voltmeter.

  Repair: There is a problem with the ECM. Perform the following procedure:

  1. Temporarily connect a test ECM.

     Refer to Troubleshooting, "Replacing the ECM".

  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.

  STOP