C4.4 and C6.6 Industrial Engines and Engines for Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot the system under the following conditions:

• There is an active diagnostic code or a recently logged diagnostic code that is related to the following:

• 0091-02 Throttle Position Sensor erratic, intermittent, or incorrect

• 0774-02 Secondary Throttle Position Sensor erratic, intermittent, or incorrect

Check that the software configuration in the Electronic Control Module (ECM) is correct for a multi-position throttle .

If the engine has an analog throttle with an Idle Validation Switch (IVS), then refer to Troubleshooting, "Idle Validation Switch Circuit - Test".

The throttle switch provides the operator with the ability to select the desired engine speed. The throttle switch configuration may be selected between 0 to 4 switches. A multi-position rotary switch may be used.

The throttle switch is typically connected to the four throttle inputs of the ECM. Each position generates a specific ON/OFF pattern on the throttle inputs. A diagnostic code is generated if a pattern that does not correspond with any of the switch positions is detected.

Once a diagnostic code is generated, the ECM ignores the throttle input signals. The desired engine speed is set to low idle if no alternative throttle is detected.

Voltage at the throttle inputs to the ECM should be 13.8 ± 0.5 Volts DC when the throttle inputs are open. The voltage should be less than 0.5 Volts DC when the throttle inputs are closed.

Illustration 1	g01806833
Schematic for the circuit for the throttle switch

Illustration 2	g01806834
Typical view of the pin locations on the P1 connector for the throttle switch (35) Switch return (49) Throttle position switch 4 (50) Throttle position switch 3 (51) Throttle position switch 2 (52) Throttle position switch 1

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the P1 connector and any other connectors that are included in the application for this throttle switch. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the sensor connector and the ECM connector that are associated with the active diagnostic code. Refer to illustration 2.

4. Verify that the latch tab of the connector is correctly latched. Also verify that the latch tab of the connector has returned to the fully latching position.

5. Check the screw for the ECM connector for the correct torque of 5.0 N·m (44 lb in).

6. Check the harness for corrosion, abrasion, and pinch points from the throttle switch to the ECM.

Expected Result:

All connectors, pins, and sockets should be completely inserted and coupled. The harness should be free of corrosion, abrasion and pinch points.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Repair the circuit.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the problem.

  STOP

Test Step 2. Check "Throttle Cab Switch Position" on the Electronic Service Tool

1. Connect the electronic service tool to the diagnostic connector.

2. Turn the keyswitch to the ON position.

3. Observe the status of the throttle switch and the throttle inputs on the electronic service tool while you operate the throttle switch in each position.

Results:

• OK - The throttle switch is functioning correctly at this time.

  Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the fault is intermittent.

  STOP

• Not OK - Record the suspect input. Proceed to Test Step 3.

Test Step 3. Jumper the Switch Input at the Throttle Switch Connector

1. Disconnect the P503 connector for the throttle switch.

2. Observe the status of the suspect throttle input on the electronic service tool.

3. Use a suitable jumper wire to short P503:1 to the terminal for the suspect throttle input at throttle switch connector P503.

4. Observe the status of the suspect throttle input on the electronic service tool.

5. Remove the jumper wire.

Expected Result:

The status of the suspect throttle input should be OFF when throttle switch connector J503/P503 is disconnected. The status should be ON when the jumper wire is installed.

Results:

• OK - The harness and the ECM are OK.

  Repair: Replace the throttle switch.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

• Not OK - Proceed to Test Step 4.

Test Step 4. Check for Shorts in the Harness

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector and the P503 connector.

3. Measure the resistance between engine ground and the terminal for the suspect throttle input at the P503 connector.

4. Measure the resistance between the terminal for the suspect throttle input on the P503 connector and the remaining terminals at the connector.

Expected Result:

Resistance should be greater than 20,000 Ohms for each reading.

Results:

• OK - Proceed to Test Step 5.

• Not OK - There is a short in the harness between the ECM and the throttle switch.

  Repair: Repair the circuit.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

Test Step 5. Check Resistance through the Harness

1. Use a jumper wire to short P503:1 to the terminal of the suspect throttle input at the P503 connector.

2. Measure the resistance between P1:35 and the terminal for the suspect throttle input at ECM connector P1 connector.

Expected Result:

Resistance should be less than 10 Ohms.

Results:

• OK - Proceed to Test Step 6.

• Not OK - There is an open circuit or excessive resistance in the harness.

  Repair: Repair the circuit.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

Test Step 6. Check the Harness and the ECM

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector and remove the wire for the suspect throttle input from the P1 connector.

3. Reconnect all of the connectors.

4. Turn the keyswitch to the ON position.

5. Observe the status of the suspect throttle input on the electronic service tool.

6. Turn the keyswitch to the OFF position.

7. Disconnect P1 connector and remove the wire from P1:35.

8. Fabricate a jumper wire with pins at both ends. Insert the jumper wire at P1:35 and the suspect throttle input at ECM connector P1 connector.

9. Reconnect all of the connectors.

10. Turn the keyswitch to the ON position.

    Note: Additional diagnostic codes will be generated because P1:35 will no longer be connected to other sensors and switches. Ignore the codes and clear the codes when you complete this test.

11. Observe the status of the suspect throttle input on the electronic service tool.

12. Turn the keyswitch to the OFF position.

13. Remove the jumper wire from the P1 connector and reconnect all wires and connectors.

Expected Result:

The status of the suspect throttle input should be OFF when the throttle input is open. The status should be ON when the jumper wire is installed.

Results:

• OK - There is a fault in the harness between the ECM and the throttle switch.

  Repair: Repair the circuit.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

• Not OK - The switch signal appears at the ECM. The ECM is not reading the switch correctly.

  Repair: Perform the following repair:

  1. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

  2. Contact the Technical Communicator.

     Note: This consultation can greatly reduce the repair time.

  3. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

  4. Use the electronic service tool to recheck the system for active diagnostic codes.

  5. If the fault is resolved with the test ECM, reconnect the suspect ECM.

  6. If the fault returns with the suspect ECM, replace the ECM.

  7. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP