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

Use this procedure under the following circumstances:

• The correct supply voltage to the PTO switches is suspect.

• Operation of the PTO switches is suspect.

Note: Some applications may only have one PTO switch.

The PTO switches provide the operator with the ability to select the desired engine speed. Engine speed will decrease with increasing load. The PTO switches can be used to control the engine speed.

The engine has the following options of set speed control:

• Single speed

• No speed (no PTO control)

The PTO switches are listed below:

• P1:52 PTO Control ON or P1

• P1:50 PTO Raise/Resume

• P1:51 PTO Set or Lower

• P1:49 (Clutch or Brake) PTO Disengage Switches

An indicator lamp is used to indicate the status of the PTO.

Illustration 1	g01805393
Schematic for the PTO switches

Illustration 2	g01805477
View of the pin locations on the P1 connector for the PTO mode switches (35) Switch Ground (GND) (49) PTO mode - disengage (50) PTO mode - raise/resume (51) PTO mode - set/lower (52) PTO mode - ON/OFF

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the J1/P1 connectors on the Electronic Control Module (ECM), the switch connections and battery connections. 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 PTO mode switches 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 fault.

  STOP

Test Step 2. Check the "PTO Mode Switches" on the Electronic Service Tool

1. Turn the keyswitch to the OFF position.

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

3. Turn the keyswitch to the ON position.

4. Observe the status of the PTO mode switch on the electronic service tool while you operate the "PTO ON/OFF switch" from the ON position to the OFF position.

5. Use the electronic service tool in order to observe the status of the PTO mode switch while you operate the "PTO Set/Lower switch" from the OFF position to the ON position.

6. Use the electronic service tool in order to observe the status of the PTO mode switch while you operate the "PTO Raise/Resume switch" from the OFF position to the ON position.

Expected Result:

Result 1 The electronic service tool will show that the "PTO mode ON/OFF switch" is in the OPEN condition when the control switch is OFF.

The electronic service tool will show that the "PTO mode ON/OFF switch" is in the CLOSED condition when the control switch is ON.

Note: The PTO mode lamp should be OFF when the switch is in the OFF position. The lamp should be flashing when the switch is in the ON position.

Result 2 When the "PTO mode Set/Lower switch" is in the OFF position the switch should be in the OPEN position.

When the "PTO mode Set/Lower switch" is in the ON position the "PTO mode Set/Lower switch" should be in the CLOSED position.

Result 3 When the "PTO mode Raise/Resume switch" is in the OFF position the display screen should show an OPEN condition.

When the "PTO mode Raise/Resume switch" is in the ON position the display screen should show a CLOSED condition.

Note: The "PTO mode lamp" will flash when the "PTO mode" is switched ON. The PTO mode lamp should change from flashing to ON when the PTO mode Set/Lower switch is CLOSED. The PTO mode lamp should change from flashing to ON when the PTO mode Raise/Resume switch is CLOSED.

Results:

• OK - The PTO mode switches operate correctly.STOP

• Not OK - Proceed to Test Step 3.

Test Step 3. Check the Status of the PTO Mode Disengage Switches

1. Use the electronic service tool in order to observe the switch status while the PTO mode disengage switches are operated OFF and ON.

   Note: The PTO mode disengage switches usually function by the operation of the brake, clutch or the operator switch. These switches should be operated separately for this test.

Expected Result:

When the PTO mode is switched ON, the electronic service tool will show that the "PTO mode disengage switches" are in the "ENGAGED" position. If the "PTO mode disengage switches" is activated, the electronic service tool will show the status of the "PTO mode disengage switches". If the "PTO mode disengage switches" are activated, the electronic service tool will show that the "PTO mode disengage switches" are in the "DISENGAGED" position.

Results:

• OK - The "PTO mode disengage switches" operate correctly.STOP

• Not OK - Proceed to Test Step 4.

Test Step 4. Check the Suspect PTO Switch

1. Turn the keyswitch to the OFF position.

2. Remove the two wires from the suspect switch. Use a suitable jumper in order to join the two wires together.

3. Turn the keyswitch to the ON position.

4. Monitor the status screen on the electronic service tool while the jumper wire is being disconnected and reconnected.

Expected Result:

When the jumper wire is connected the status of the PTO mode switches should be "CLOSED".

When the jumper wire is disconnected the status of the PTO mode switches should be "OPEN".

Results:

• OK - The switch is faulty.

  Repair: Replace the switch.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair has eliminated the problem.

  STOP

• Not OK - There is a fault with the harness between the PTO mode switches and the engine ECM. Proceed to Test Step 5.

Test Step 5. Measure the Resistance of the Cables at the ECM

1. Turn the keyswitch to the OFF position.

2. Connect the cables to the suspect switch.

3. Disconnect the P1 connector from the ECM.

4. Measure the resistance between P1:35 and the appropriate pin on the P1 connector for the suspect switch. Refer to illustration 1.

5. Repeat the procedure for each of the PTO mode switches.

Expected Result:

The measured resistance should be less than 10 Ohms with the switch ON.

The measured resistance should be more than 20,000 Ohms with the switch OFF.

Results:

• OK - Proceed to Test Step 6.

• Not OK - There is a fault with the wires between the suspect switch and the P1 connector.

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

  STOP

Test Step 6. Test the Engine ECM

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector from the ECM.

3. By using a suitable pin removal tool, temporarily remove the wires from the suspect switch socket. By using a suitable pin removal tool, temporarily remove the wires from the P1:35.

4. Insert a jumper wire between the suspect switch socket and P1:35.

5. Turn the keyswitch to the ON position.

6. Monitor the status screen on the electronic service tool while the jumper wire is being disconnected and reconnected.

Expected Result:

The status screen should display an OPEN condition with the switch in the OFF position.

The status screen should display a CLOSED condition with the switch in the ON position.

Results:

• OK - The ECM is working correctly.STOP

• Not OK - The ECM is not working 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