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Compression Brake Solenoid Circuit. Location of the compression brake solenoid. Schematic for the compression brake circuit, страница 6

  1. Turn the keyswitch to ON position.
  1. Check the status for the compression brake switch on Cat ET.
  1. Remove the jumper wire.
  1. Check the status for the compression brake switch on Cat ET.
  1. Turn the keyswitch to the OFF position.

Expected Result:

The status for the compression brake switch indicates "Automatic" when a jumper wire is installed between terminal 2 and terminal 3.

The status for the compression brake switch indicates "Off" when a jumper wire is removed from terminal 2 and terminal 3.

Results:

  • OK - The status changed accordingly.

Repair: Temporarily replace the switch. Verify that the new switch solves the problem before you permanently install the new switch.

STOP

  • Not OK - The status did not change accordingly. Proceed to Test Step11.

Test Step 11. Check for Shorts in the Wiring Harness

  1. Turn the keyswitch to OFF position.
  1. Disconnect ECM connectors P1and P2.
  1. Measure the resistance between P1-34 and every terminal on ECM connector P1 and ECM connector P2.

Expected Result:

The measured resistance indicates an open circuit.

Results:

  • OK - The resistance measurement indicates an open circuit. Proceed to Test Step 12.
  • Not OK - The resistance measurement indicates a short circuit.

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

STOP

Test Step 12. Check for an Open in Wiring Harness

  1. Disconnect the connector for the compression brake switch.
  1. Short the wires of the compression brake switch at the compression brake switch. Insert a jumper wire between the following terminals of the connector for the harness side:
    • Terminal 2
    • Terminal 3
  1. Measure the resistance between J1-34 and J1-45 at the ECM connectors.

Expected Result:

The measured resistance indicates a short circuit.

Results:

  • OK - The resistance measurement indicates a short circuit. Proceed to Test Step13.
  • Not OK - The resistance measurement indicates an open circuit. There is an open circuit or excessive resistance in the wiring harness.

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

STOP

Test Step 13. Short the Input Wires of the Compression Brake Switch at the ECM Connector

  1. Disconnect the J1 ECM connector.
  1. Remove the wires from J1-34 compression brake switch input and J1-45 sensor return.
  1. Fabricate two jumper wires with sockets on one end and insert one into J1-34 and J1-45.
  1. Connect a jumper wire between the jumper wires in J1-34 and J1-45.
  1. Reconnect the J1 ECM connector.
  1. Turn the keyswitch to the ON position.
  1. Check the status for the compression brake switch on Cat ET.
  1. Disconnect the jumper wire between the jumper wires in J1-34 and J1-45.

Note: Ensure that the jumper wires are electrically isolated from all contact.

  1. Check the status for the compression brake switch on Cat ET.
  1. Turn the keyswitch to OFF position.

Expected Result:

The status for the compression brake switch indicates "Automatic" when a jumper wire is installed between jumper wires J1-34 and J1-45.

The status for the compression brake switch indicates "Off" when a jumper wire is removed between jumper wires J1-34 andJ1-45.

Results:

  • OK - The status changed accordingly.

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

STOP

  • Not OK - The status did not change accordingly.

Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

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