C7.1 Industrial Engine and Generator Set Caterpillar

This procedure covers the following codes:

If a fault occurs with the primary throttle and a secondary throttle is installed, the engine will use the secondary throttle until the fault is repaired.

If a fault occurs with the secondary throttle, the engine will use the primary throttle until the fault is repaired.

If a functional throttle is not available, the following conditions will occur:

• The engine will default to the limp home speed.

• If the engine speed is higher than the limp home speed, the engine will decelerate to the limp home speed.

• If the engine speed is lower than the limp home speed, the engine speed will remain at the current speed.

• The engine will remain at this speed while the diagnostic code remains active.

• All inputs from the faulty throttle are ignored by the ECM until the fault is repaired.

• All inputs from the repaired throttle will be ignored by the ECM until the keyswitch has been cycled.

The diagnostic codes above relate to an analog sensor. Use this procedure only if the analog sensor uses an output from a variable resistor.

The sensor is most likely to be mounted on a throttle pedal. The sensor is attached directly to the throttle assembly. The sensor provides an output voltage to the ECM. The sensor output voltage will vary with the position of the throttle. Foot operated or hand operated throttle assemblies are available.

The sensor receives +5 VDC power from the ECM. The sensor will produce a raw signal voltage that will alter between low idle and high idle. The voltage is changed into a throttle position within the range 0% to 100% by the ECM.

The sensor senses the speed requirement from the throttle position. A second sensor may override this speed requirement from the first sensor. This override will be subject to an input from a secondary throttle or from the SAE J1939 (CAN) data link or from a PTO control.

Use the electronic service tool in order to check the input status.

Illustration 1	g02158591
Schematic of the analog throttle position sensors

Illustration 2	g01980913
Typical example of the P1 pin locations for the analog throttle position sensor (1) Throttle 2 position (2) 5 VDC supply (3) Ground (66) Throttle 1 position

Test Step 1. Check for Connector Damage

1. Turn the keyswitch to the OFF position.

2. Check the connectors and the harness for the following faults: damage, abrasion, corrosion and incorrect attachment.

3. Refer to Troubleshooting, "Electrical Connectors - Inspect".

4. Perform a 45 N (10 lb) pull test on each of the wires in the harness that are associated with the throttle position sensor. Check the wire connectors at the ECM and at the throttle sensor. The wire connectors are shown in Illustration 1.

5. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in).

Expected Result:

The connectors and the harness should be free of the following faults: damage, abrasion, corrosion and incorrect attachment.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Repair the connectors or the harness and/or replace the connectors or the harness.

  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 2. Check for Active Diagnostic Codes

1. Turn the keyswitch to the ON position.

2. Use the electronic service tool to check for diagnostic codes.

Expected Result:

One or more of the diagnostic codes that are listed in Table 1 is active or recently logged.

Results:

• One or more of the preceding diagnostic codes is active or recently logged. - Proceed to Test Step 3.

• There are no active or recently logged diagnostic codes for the analog throttle position sensors. - Proceed to Test Step 5.

Test Step 3. Check the Throttle Position with the Electronic Service Tool

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

2. Turn the keyswitch to the ON position. Do not start the engine.

3. Observe the throttle position reading on the electronic service tool.

4. Operate the throttle over the full range of movement.

Expected Result:

The output should increase when the throttle is increased.

The output should be between "20 percent" and "27 percent" at the low idle position. The output should be between "80 percent" and "87 percent" at the high idle position.

Results:

• OK - The sensor is operating correctly. Proceed to Test Step 4.

• Not OK - The ECM is not receiving a correct signal from the sensor. Proceed to Test Step 5.

Test Step 4. Check the Throttle Selection Status with the Electronic Service Tool

1. Check the status of the throttle selection switch (if equipped). Use the electronic service tool in order to check the status of the throttle selection switch.

Expected Result:

If the status of the throttle selection switch is shown in the OFF position, then the throttle 1 has control of the engine speed.

If the throttle selection switch status is shown in the ON position, then the throttle 2 has control of the engine speed.

The throttle may be overridden by using the SAE J1939 (CAN) data link or a PTO control.

Results:

• OK - The throttle selection switch is operating correctly.

  Repair: There may be an intermittent fault. Refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The wrong throttle is selected. Change to the other throttle. There may be a fault with the selector switch input.

  Repair: Check the connections between the throttle selection switch and P1:70 and P1:64. Refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

Test Step 5. Check the Voltage at the Sensor

1. Turn the keyswitch to the OFF position.

2. Install a breakout "T" with three terminals to the sensor.

3. Turn the keyswitch to the ON position.

4. Measure the voltage between terminal "A" and terminal "B" on the breakout "T".

Expected Result:

The supply voltage should be between 4.84 VDC and 5.16 VDC.

Results:

• OK - The supply voltage is reaching the sensor. Proceed to Test Step 6.

• Not OK - The supply voltage is not reaching the sensor.

  Repair: Refer to Troubleshooting, "5 Volt Sensor Supply Circuit - Test".

  STOP

Test Step 6. Check the Position of the Sensor

1. Turn the keyswitch to the OFF position.

2. Install a breakout "T" with three terminals to the sensor.

3. Turn the keyswitch to the ON position.

4. Measure the voltage between terminal "C" and terminal "B" on the breakout "T".

5. Observe the voltage while the engine speed control is moved from the minimum to the maximum position.

Expected Result:

The voltage should vary between 1.5 VDC and 4.4 VDC when the speed control is moved from the minimum to the maximum position.

Results:

• OK - The throttle position sensor is operating correctly. Proceed to Test Step 7.

• Not OK - The throttle position sensor is faulty. Proceed to Test Step 8.

Test Step 7. Check the Sensor at the ECM

1. Turn the keyswitch to the OFF position.

2. Remove the P1 connector.

3. Temporarily remove pin P1:66 from the connector.

4. Reconnect the P1 connector.

5. Connect the red probe of a multimeter to the removed pin and the black probe of the multimeter to P1:3.

6. Turn the keyswitch to the ON position.

7. Use the multimeter to display the output voltage of the sensor while the engine speed control is moved from the minimum position to the maximum position.

8. Turn the keyswitch to the OFF position.

9. Remove the P1 connector and reinstall P1:66.

10. Reconnect the P1 connector.

Expected Result:

The output from the throttle position sensor is 0.5 VDC or less with the sensor slot in the released position.

The output from the throttle position sensor is 4.5 VDC or more with the sensor slot in the advanced position.

Results:

• OK - The ECM terminals have the correct voltage for the sensor.

  Repair: Check for the correct supply voltage at the ECM. If the voltage is correct, then perform the following procedure.

  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 at a Caterpillar dealer.

     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

• Not OK - There is a fault in the harness or the connectors between the sensor and the ECM. Check all of the connections between the ECM and the sensor. Repair the damaged cables or replace the damaged cables. Check that the repairs have eliminated the fault.

  STOP

Test Step 8. Remove the Sensor from the Engine Speed Control Assembly

Illustration 3	g01170704
Throttle pedal assembly (1) Sensor mounting face (2) Sensor drive key (3) Mounting screw holes

Illustration 4	g01170753
Throttle block assembly (1) Mounting screw holes (2) Sensor drive slot (3) Sensor mounting face

1. Turn the keyswitch to the OFF position.

2. Record the position of the sensor and then remove the sensor.

3. Remove the sensor from the housing and inspect the cables for signs of wear.

4. Connect a multimeter to terminal "C" and terminal "B" of the breakout "T".

5. Turn the keyswitch to the ON position.

6. Record the signal voltage of the sensor with the sensor slot in the released position.

7. Record the signal voltage of the sensor with the sensor slot in the advanced position.

Expected Result:

The output from the sensor is 0.5 VDC or less with the sensor slot in the released position.

The output from the sensor is 4.5 VDC or more with the sensor slot in the advanced position.

Results:

• OK -

  Repair: The operation of the sensor is correct. The fault is caused by the foot pedal or the lever assembly. Adjust the assembly or replace the assembly.

  Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repairs have eliminated the fault.

  STOP

• Not OK - The sensor is faulty.

  Repair: Replace the sensor.

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

  STOP