C7.1 Industrial Engine and Generator Set Caterpillar


Mode Selection Circuit - Test

Usage:

C7.1 770
System Operation Description:

This procedure covers the following code:

Table 1
Diagnostic Trouble Codes for the Circuit for Mode Selection 
J1939 Code  Description  Notes 
2882-2  Engine Alternate Rating Select : Erratic, Intermittent, or Incorrect  The Electronic Control Module (ECM) detects a combination of switch positions for the mode switches that has not been defined.
If equipped, the warning lamp will come on and the ECM will log the diagnostic code.
The ECM will return the engine to the last good mode selection or setting.
The engine will start and the engine will default to the previous mode selection. The engine may operate at reduced speed or reduced power depending on the mode that is selected. 

Use this procedure to check if the mode selector switch operates correctly.

The mode selector switch inputs provide the operator with the ability to select a maximum of four different modes of operation. Different modes of operation can be used giving the operator a means to select the most efficient method of completing the required work.

Each mode has a single fuel limit map, a rated speed, and a matched fuel delivery. Each mode also has a specific droop value for throttle 1 and throttle 2.

Table 2
Mode Number  Switch 2  Switch 1  Enabled 
Open  Open  Y/N 
Open  Closed  Y/N 
Closed  Open  Y/N 
Closed  Closed  Y/N 

If an open or short circuit condition occurs in the circuit for switch 1 or switch 2, the mode of operation will be different to the mode that was selected by the operator. If the mode of operation is not enabled on the application, a 2882-2 diagnostic code will become active.



Illustration 1g02129713
Typical schematic for the mode selector switches


Illustration 2g02129720
View of the pin locations on the P1 connector for the circuit for mode selection
(62) Mode switch 1
(64) Mode switch 2

Test Step 1. Inspect Electrical Connectors and Wiring

  1. Turn the keyswitch OFF.

  2. Thoroughly inspect the P1 connector. Thoroughly inspect the mode switch connectors, plugs, and interconnections on the harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

  3. Perform a 45 N (10 lb) pull test on each of the wires in the P1 connector that are associated with the mode selector switches.

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

  5. Check the harness for abrasions and for pinch points from the battery to the ECM.

Results:

  • OK - Proceed to Test Step 2.

  • Not OK -

    Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are correctly connected.

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

    STOP

  • - If the fault has not been eliminated proceed to Test Step 2.

Test Step 2. Check the Status of the Mode Selector Switch

  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. Monitor the status screen on the electronic service tool. Cycle the mode switch to the ON position and to the OFF position.

Results:

  • The switch status changes as you cycle the mode switches. When the switch is in the OFF position, the switch is open. When the switch is in the ON position, the switch is closed. -

    Repair: Verify that the status of the switch changes as the switch is cycled.

    STOP

  • The switch status does not change as you cycle the mode switches - There is a fault with the circuit for the mode selector switch. Proceed to Test Step 3.

Test Step 3. Insert a Jumper at the Suspect Mode Switch

  1. Turn the keyswitch to the OFF position.

  2. Perform the following procedure to test the circuit of mode selector switch No. 1. Place a jumper wire across the contacts of switch No. 1.

  3. Perform the following procedure to test the circuit of mode selector switch No. 2. Place a jumper wire across the contacts of switch No. 2.

  4. Turn the keyswitch to the ON position. Monitor the status screen on the electronic service tool. Connect the jumper wire and then disconnect the jumper wire.

Expected Result:

When the jumper wire is connected, the switch should be in the CLOSED position.

Results:

  • When the jumper wire is connected, the switch is in the CLOSED position. -

    Repair: Verify that the jumper wire has been removed. The suspect mode selector switch is faulty. Replace the switch and verify that the repair has eliminated the fault.

    STOP

  • When the jumper wire is connected, the switch is in the OPEN position - Proceed to Test Step 4.

Test Step 4. Measure the Voltage at the Switch

  1. Turn the keyswitch to the OFF position.

  2. Use the electronic service tool to turn both of the mode switches to the ON position.

  3. Turn the keyswitch to the ON position.

  4. Measure the voltage from the input or the output of each mode switch to a suitable ground.

Expected Result:

For 12 V systems, the measured voltage should be a constant 11.0 to 13.5 VDC.

For 24 V systems, the measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

  • OK - The measured voltages are within the expected range. The wiring between the mode switches and switched battery+ is OK. Proceed to Test Step 5.

  • Not OK - One of the measured voltages is not within the expected range. The fault is in the wiring between switched battery+ and the mode switch with the incorrect voltage.

    Repair: Repair the faulty wiring or replace the faulty wiring.

    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 5. Measure the Voltage at the ECM

  1. Turn the keyswitch to the OFF position.

  2. Use the electronic service tool to turn both of the mode switches to the ON position.

  3. Turn the keyswitch to the ON position.

  4. Measure the voltage from P1:62 to a suitable ground.

  5. Measure the voltage from P1:64 to a suitable ground.

Expected Result:

For 12 V systems, the measured voltage should be a constant 11.0 to 13.5 VDC.

For 24 V systems, the measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

  • OK - The measured voltages are within the expected range. There may be a fault with the ECM.

    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 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 - One of the measured voltages is not within the expected range. The fault is in the wiring between the ECM and the mode switch with the incorrect voltage.

    Repair: Repair the faulty wiring or replace the faulty wiring.

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

    STOP

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