3500B Industrial Engines Caterpillar

The Intermediate Speed Switch is a normally open switch. When this switch is closed, the engine speed will decrease to the customer programmable intermediate idle speed. This intermediate speed is the speed rate of the PTO. This will happen regardless of PTO set speed or the desired speed for the throttle position sensor. When the intermediate speed switch is opened, the engine speed will be increased back to the desired engine speed for the throttle or the desired engine speed for PTO operation according to the ramp rate for the PTO speed. If the intermediate idle speed is programmed above the current desired engine speed for the throttle or the desired engine speed for PTO operation, this switch will have no effect on engine speed.

Illustration 1	g00751411

Test Step 1. Check the Electrical Connectors and the Wiring.

1. Turn the Battery switch for the ECM to the OFF position.

2. Turn the breaker at the battery to the OFF position.

3. Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to Troubleshooting, "Inspecting Electrical Connectors" for details.

4. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.

5. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

6. Check the customer connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).

7. Check the harness and the wiring for abrasion and pinch points.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring should be free of corrosion, abrasion or pinch points.

Results:

• OK - The wiring and connectors are okay. Proceed to Test Step 2.

• Not OK - Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected. Verify that the repair eliminates the problem.STOP

Test Step 2. Check the Circuit of the Intermediate Speed Switch on the ET.

1. Install the ET to the service tool connector.

2. Turn the breaker at the battery to the ON position.

3. Turn the Battery switch for the ECM to the ON position.

4. Operate the intermediate speed switch. Observe the status for the intermediate speed switch on the ET.

Expected Result:

The status of the intermediate speed switch should read "ON" with the intermediate speed switch in the Closed position. The status of the intermediate speed should read "OFF" when the intermediate speed switch is in the Open position.

Results:

• OK - The circuit of the intermediate speed switch is operating normally.STOP

• Not OK - The circuit of the intermediate speed switch is not operating normally. Proceed to Test Step 3.

Test Step 3. Check the Intermediate Speed Switch.

1. Turn the Battery switch for the ECM to the OFF position.

2. Turn the intermediate speed switch to the OFF position.

3. Remove the wires from the terminals on the intermediate speed switch.

4. Connect a voltmeter between terminal 2 and terminal 3 on the intermediate speed switch.

5. Measure the resistance between terminal 2 and terminal 3 on the intermediate speed switch.

6. Turn the intermediate speed switch to the ON position.

7. Measure the resistance between terminal 2 and terminal 3 on the intermediate speed switch.

Expected Result:

The resistance should be greater than 20,000 Ohms with the intermediate speed switch in the OFF position. The resistance should be less than 10 Ohms with the intermediate speed switch in the ON position.

Results:

• OK - The resistance measurements are okay. The problem is not with the intermediate speed switch. Proceed to Test Step 4.

• Not OK - The resistance measurements are not okay. The intermediate speed switch is not operating correctly.

  Repair: Replace the intermediate speed switch. Verify that the problem is no longer present.

  STOP

Test Step 4. Check for a Short Circuit in the Wiring Harness.

1. Disconnect the ECM connectors J1/P1 and J2/P2. Disconnect the wires from the intermediate speed switch.

2. Measure the resistance between P1-29 and the engine ground.

3. Measure the resistance between P2-01 and the engine ground.

4. Measure the resistance between P1-29 and P2-01.

Expected Result:

The resistance should be greater than 20,000 Ohms.

Results:

• OK - The resistance is greater than 20,000 Ohms. Proceed to Test Step 5.

• Not OK - The resistance is less than 20,000 Ohms. There is a short in the harness between the switch and the ECM.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the problem is no longer present.

  STOP

Test Step 5. Check the Wiring Harness for an Open Circuit.

1. Short the wires from the intermediate speed switch together at the intermediate speed switch.

2. Measure the resistance between P1-29 and P2-01 at the ECM connectors.

3. Replace all wires and remove all shorts.

Expected Result:

The resistance should be less than 10 Ohms.

Results:

• OK - The resistance is less than 10 Ohms. Proceed to Test Step 6.

• Not OK - The resistance is greater than 10 Ohms. There is an open or excessive resistance in the harness.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the problem is no longer present.

  STOP

Test Step 6. Short the Inputs from the Intermediate Speed Switch together at the ECM.

1. Disconnect the ECM connectors J1/P1 and J2/P2.

2. Install a Breakout T to the ECM connectors J1/P1 and J2/P2.

3. Remove wire P1-29 from the Breakout T on ECM connector P1.

4. Remove wire P2-01 from the Breakout T on ECM connector P2.

5. Turn the Battery switch for the ECM to the ON position.

6. Observe the status of the intermediate speed switch on the ET.

7. Short the wires from P1-29 and P2-01 together.

8. Observe the status of the intermediate speed switch on the ET.

9. Turn the Battery switch for the ECM to the OFF position.

Expected Result:

The status of the intermediate speed switch changes to On when the wires are shorted together. The status of the intermediate speed switch changes to Off when the wires are disconnected.

Results:

• OK - The status of the intermediate speed switch changes to On when the wires are shorted together. The status of the intermediate speed switch changes to Off when the wires are disconnected. The circuit for the intermediate speed switch has an intermittent problem.

  Repair: Repair the circuit connectors or wiring and/or replace the circuit connectors or wiring.

  STOP

• Not OK - The ECM is not reading the inputs from the intermediate speed switch correctly.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM".

  STOP