G3500 A3 Engines Caterpillar

Use this procedure to troubleshoot the following diagnostic codes:

• 1440-9 Throttle Actuator abnormal update rate

• 1440-12 Throttle Actuator failure

The throttle actuator is an electronic actuator that works with the Electronic Control Module (ECM) in order to ensure the correct position of the throttle in all conditions of engine operation.

The ECM and the throttle actuator communicate via the CAN data link. The ECM sends a command signal to the actuator. The actuator sends the following information to the ECM:

• Actuator position

• Heartbeat signal for the Customer Communication Module (CCM)

• Software version

• Internal fault diagnosis

If the ECM cannot communicate with the throttle actuator, the ECM activates a 1440-9 diagnostic code and the engine is shut down. A 1440-9 diagnostic code is probably caused by a problem with an electrical connector or a harness. The next likely cause is a problem with the actuator. The least likely cause is a problem with the ECM.

Terminating resistors must be connected to each end of the CAN data link. The terminating resistors improve the communication between the devices. If there is an intermittent diagnostic code for any of the devices that are connected to the CAN data link, be sure to check the terminating resistors. One of the terminating resistors is connected to a splice in the wiring harness near the J1/P1 ECM connector. The other terminating resistor is connected to a "T" inside the optional remote panel. If the engine is not equipped with a remote panel, the other terminating resistor will be connected at the far end of interconnect harness. Refer to the appropriate documentation for the site in order to determine the location of this resistor.

This troubleshooting procedure may generate additional diagnostic codes. Correct the cause of the original diagnostic code before continuing. You clear the diagnostic codes after the problem is resolved.

Illustration 1	g01437479
Schematic for the circuit of the throttle actuator

Test Step 1. Inspect the Electrical Connectors and the Wiring

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

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

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   Illustration 2	g02341756
   Location of the components for the throttle actuator (typical example) (1) J1/P1 ECM connectors (2) Throttle actuator (3) Interface box

2. Thoroughly inspect ECM connectors (1), the connectors for actuator (2), and the connectors at the interface box (3).

   1. Check the allen head screw for each of the ECM connectors for the proper torque.
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      Illustration 3	g01391850
      Terminal locations at the P1 ECM connector for the throttle actuator (34) CAN data link − (42) Shield (50) CAN data link +

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      Illustration 4	g02341758
      Terminal locations at the connector for the throttle actuator (C) Shield for the CAN data link (F) Keyswitch (G) CAN data link− (M) CAN data link+ (Q) −Battery (Z) +Battery

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      Illustration 5	g01392608
      Terminal locations at the interface box for the throttle actuator (7) Keyswitch (9) −Battery (F1) Main fuse (15 Amp) (F2) Fuse for the throttle actuator (10 Amp)

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the throttle actuator.

   3. Check the wiring for abrasion and for pinch points from the throttle actuator to the ECM.

Expected Result:

All of the 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. Ensure that all of the seals are properly installed. Ensure that the connectors are properly engaged. Verify that the repair has eliminated the original problem.

  STOP

Test Step 2. Check for Diagnostic Codes

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

2. Look for the following diagnostic codes:

   • 1440-9 Throttle Actuator abnormal update rate

   • 1440-12 Throttle Actuator failure

Expected Result:

There is not an active diagnostic code for the throttle actuator at this time.

Results:

• OK - There is not an active diagnostic code for the throttle actuator at this time.

  Repair: There does not seem to be an electrical problem with the throttle actuator. If one of the codes is logged, there may be an intermittent problem in the harness or in a connector. There may be a problem with one of the fuses in the circuit.

  Check that electrical power is available at the throttle actuator. If an intermittent problem with the harness or a connector is suspected, refer to Troubleshooting, "Inspecting Electrical Connectors" for information that is related to troubleshooting intermittent electrical problems.

  STOP

• Not OK - 1440-9 is active - The ECM has detected a problem with the communication between the ECM and the throttle actuator. Proceed to Test Step 3.

• Not OK - 1440-12 is active - There is a problem with the throttle actuator.

  Repair: Replace the throttle actuator. Verify that the problem is resolved.

  STOP

Test Step 3. Check for Electrical Power at the Throttle Actuator

1. Refer to Illustration 1. Measure the voltage for the throttle actuator at the engine interface box.

   The battery voltage must be between 18 V and 32 V in order for the throttle actuator to operate correctly. If a problem exists, correct the problem before you continue.

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

3. Disconnect the harness connector for the throttle actuator.

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

5. At the harness connector for the actuator, measure the voltage between the following terminals:

   • F and Q (keyswitch power)

   • Z and Q (battery power)

Results:

• OK - Both voltages at the harness connector are within 2 V of the voltage at the engine power distribution box. Proceed to Test Step 4

• Not OK - At least one of the voltages are not within 2 V of the voltage at the engine power distribution box.

  Repair: The throttle actuator is not receiving the proper operating voltage. There is a problem in the harness or in a connector. Determine the cause of the excessive voltage drop. Perform the necessary repairs. Verify that the repair eliminates the original problem.

  STOP

Test Step 4. Check the Resistance of the CAN Data Link at the Harness Connector for the Throttle Actuator

Note: When the resistance measures between 114 Ohms and 126 Ohms, one of the resistors is not properly connected into the circuit.

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

2. Disconnect the harness connector for the throttle actuator.

3. Measure the resistance between terminals M and G of the harness connector for the throttle actuator.

Results:

• OK - The resistance is between 57 and 63 Ohms. Proceed to Test Step 5

• Not OK - The resistance is not between 57 Ohms and 63 Ohms.

  Repair: Ensure that 2 termination resistors of the correct value are in place and properly connected to the circuit.

  Proceed to Test Step 5

Test Step 5. Check the Resistance of the CAN Data Link at the P1 ECM Connector

Note: Some devices will be spliced into the harness at different locations. Therefore also verify the correct resistance at the ECM. The ECM is the device the components are communicating with and the device that is presenting the code. Measure resistance at the ECM and check for continuity with the suspect device on the data link.

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

2. Disconnect the ECM J1/P1 connectors.

3. Measure the resistance between terminals P1-50 (CAN data link +) and P1-34 (CAN data link -).

Results:

• OK - The resistance is between 57 and 63 Ohms. Proceed to Test Step 6

• Not OK - The resistance is not between 57 Ohms and 63 Ohms.

  Repair: Ensure that 2 termination resistors of the correct value are in place and properly connected to P1-50 and P1-34.

  Proceed to Test Step 6

Test Step 6. Check the Continuity of the Wiring Harness for the CAN Data Link

1. Use a multimeter to check for continuity between the points that are listed in Table 1.
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   Table 1

   P1-34	Terminal G of the harness connector for the throttle actuator
   P1-50	Terminal M of the harness connector for the throttle actuator

Results:

• OK - There is continuity between the terminals of the connectors. Proceed to Test Step 7.

• Not OK - There is an open circuit between the terminals of the connectors.

  Repair: Perform the necessary repairs to the wiring and/or connectors. Replace parts, if necessary. Ensure that all of the seals are properly installed. Ensure that the connectors are properly engaged. Verify that the repair has eliminated the original problem.

  STOP

Test Step 7. Check the Harness for a Short Circuit

1. Measure the resistance between the points that are listed in Table 2. Be sure to wiggle the wires in the harnesses as you make each resistance measurement.
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   Table 2

   P1-34	All of the other terminals on the P1 connector
   	Ground strap for the ECM
   P1-50	All of the other terminals on the P1 connector
   	Ground strap for the ECM

Results:

• OK - Each check of the resistance indicates an open circuit. The harness is not shorted. Proceed to Test Step 8.

• Not OK - At least one check of the resistance indicates that there is continuity.

  Repair: There is a short circuit in a harness. There may be a problem with a connector. Repair the wiring and/or the connector. Replace part, if necessary. Restore the wiring to the original configuration. Verify that the problem is resolved.

  STOP

Test Step 8. Determine if the ECM is the Problem

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

2. Temporarily install a new ECM.

3. Connect the throttle actuator.

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

5. Check for proper operation.

Results:

• OK - The new ECM resolved the problem.

  Repair: 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, "ECM - Replace"

  STOP

• Not OK - The new ECM did not resolve the problem. Proceed to Test Step 9

Test Step 9. Determine if the Throttle Actuator is the Problem

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

2. Temporarily install a new throttle actuator.

3. Restore electrical power to the ECM. Set the engine control to the STOP mode.

4. Check for proper operation.

Results:

• OK - The new actuator resolved the problem.

  Repair: Permanently install the new throttle actuator.

  STOP

• Not OK - The problem is not resolved.

  Repair: Retest the system.

  STOP