C7 Engine for the AP-755 Asphalt Paver and the PM-102 Cold Planer Caterpillar

This procedure covers the 91-02 Incorrect Throttle Switch inputs.

The throttle switch provides the operator with the ability to select the desired engine speed. The throttle switch is a two-position select switch. The two positions are indicated with device status icons that represent the high idle position (Rabbit) and the low idle position (Tortoise). The throttle switch is used to select high idle or low idle for the engine.

High Idle - To increase engine speed to high idle, place the switch in the Rabbit position.

Low Idle - To decrease engine speed to low idle, place the switch in the Tortoise position.

The engine will start while the throttle switch is in the Rabbit position. However, the Electronic Control Module (ECM) will ignore the state of the switch until the switch is toggled to the Tortoise position. The switch must then be returned to the high idle position in order for the engine ECM to process the request for the high idle engine speed.

The engine ECM determines the state of the control relay by detecting an open circuit on one of the inputs and a ground circuit on the other input. If the switch inputs are detected in the same state, then the ECM will generate a 91-02 diagnostic code.

Illustration 1	g01273905
Schematic

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove the electrical power from the ECM.

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Illustration 2	g01144470
Schematic for throttle switch

2. Thoroughly inspect the J1/P1 ECM connector. Also, thoroughly inspect all of the connectors that are between the ECM and the throttle switch. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.

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Illustration 3	g01273919
P1 ECM connector (P1-44) Throttle switch (N/O) (P1-45) Throttle switch (N/C)

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Illustration 4	g01149844
Terminal locations of the relay for the throttle switch

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

4. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for the correct torque value.

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

Expected Result:

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

Results:

• OK - The harness and wiring appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem in the connectors and/or wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check the Status of the Throttle Inputs

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore the electrical power to the ECM.

3. Observe the status of the throttle inputs on Cat ET while you operate the throttle switch in each position.

Expected Result:

The status of the throttle switch corresponds with the position of the switch.

Results:

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

  Repair: Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.

  STOP

• Not OK - One or more of the inputs is incorrect. Proceed to Test Step 3.

Test Step 3. Check the Circuit between the Engine ECM and the Relay

1. Remove the electrical power from the ECM.

2. Use Cat ET to check the condition of the circuit between the throttle switch and the relay:

   1. Disconnect the connector from the relay for the throttle switch.

   2. Use a jumper wire to connect relay terminal 30 to relay terminal 87A at the relay connector for the throttle switch. Do not connect the connector to the relay.

   3. Restore the electrical power to the ECM.

   4. Check the status of the throttle switch on Cat ET.

      The correct status of the throttle switch is low idle.

   5. Remove the jumper wire from relay terminal 87A. Install the jumper wire between relay terminal 87 and relay terminal 30.

   6. Monitor the status of the throttle switch on Cat ET.

      The correct status of the throttle switch is high idle.

3. Remove the electrical power from the ECM.

4. Remove the jumper wire. Reconnect all wires to the original configuration.

Expected Result:

The correct status of the throttle switch is displayed on Cat ET.

Results:

• OK - The ECM and the harness to the relay are OK.

  Repair: The problem is in the circuit from the relay to the throttle switch. The problem may be in the relay. Troubleshoot the remainder of the circuit for the throttle switch. Refer to the correct Schematic for your machine.

  STOP

• Not OK - Cat ET does not display the correct status for the throttle switch. The problem may be the harness to the relay or the ECM. Verify that the wire to chassis ground is not open and that the wire has a good connection to chassis ground. Proceed to Test Step 4.

Test Step 4. Check the Operation of the ECM

1. Remove the wires for the throttle inputs from the P1 ECM connector.

2. Install a 208-0059 Adapter Cable As (70-Pin Breakout) at the J1 ECM connector. Install the P1 ECM connector.

3. Use Cat ET to check the status of the throttle switch:

   1. Use a jumper wire to connect terminal 45 to terminal 61 at the breakout harness.

   2. Restore the electrical power to the ECM.

   3. Check the status of the throttle switch on Cat ET.

      The correct status of the throttle switch is low idle.

   4. Remove the jumper wire from terminal 45. Install the jumper wire between terminal 44 and terminal 61 at the breakout harness.

   5. Monitor the status of the throttle switch on Cat ET.

      The correct status of the throttle switch is high idle.

4. Remove the electrical power from the ECM.

5. Remove the jumper wire and breakout T. Reconnect all wires and connectors to the original configuration.

Expected Result:

The correct status of the throttle switch is displayed on Cat ET.

Results:

• OK - The ECM is operating properly.

  Repair: The problem is in the harness from the ECM to the relay for the throttle switch. Repair the connectors or the harness. If necessary, replace the connectors or the harness.Verify that the repair eliminates the problem.

  STOP

• Not OK - The ECM is not responding to the switch inputs.

  Repair: Verify your results. Refer to electronic Troubleshooting, "Replacing the ECM" before you replace the ECM.

  STOP