0446005 JOHNSON PLATE

Illustration 1 g01199118
Location of the compression brake solenoid (typical example)
Illustration 2 g01395529
Schematic for the compression brake circuitTest Step 1. Inspect the Electrical Connectors and the Wiring
Electrical shock hazard. The electronic unit injector system uses 90-120 volts.
Remove electrical power from the engine's ECM. A strong electrical shock hazard is present if the electrical power is not removed from the engine ECM.
Thoroughly inspect ECM connector J2/P2 and the connector for the valve cover. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 3 g01141312
P2 ECM connector (P2-1) Compression brake solenoid low/high (P2-8) Compression brake solenoid med/high (P2-14) Digital return
Illustration 4 g01395532
Valve cover connector (10) Compression brake solenoid med/high (11) Compression brake solenoid low/high (12) Digital return
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the compression brake solenoids.
Check the allen head screw for each of the ECM connectors and the machine connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasion and for pinch points from the valve cover back to the ECM.Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion, or of pinch points.Results:
OK - The harness and connectors appear to be OK. Proceed to Test Step 2.
Not OK - There is a problem with the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals for each of the connectors are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.STOPTest Step 2. Check for Active Diagnostic Codes and/or Logged Diagnostic Codes
Connect Cat ET to the service tool connector.
Turn the keyswitch to the ON position.
Access the diagnostic overrides under the "Diagnostics" menu.
Start the "Compression Brake Low/High Override" on Cat ET.
Once Cat ET displays the status of the compression brake solenoid, stop the "Compression Brake Low/High Override".
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.
Start the "Compression Brake Med/High Override" on Cat ET.
Once Cat ET displays the status of the compression brake solenoid, stop the "Compression Brake Med/High Override".
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.Expected Result:No diagnostic codes are active or logged for the compression brake.Results:
OK - No diagnostic codes are active.Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - A 791-5 diagnostic code or a 792-5 diagnostic code is active at this time. If both diagnostic codes are active, the problem is most likely in the shared return wire. Inspect the wire and/or connectors for an open circuit. Proceed to Test Step 3.
Not OK - A 791-6 diagnostic code or a 792-6 diagnostic code is active at this time. Proceed to Test Step 6.Test Step 3. Create a Short Between the Wires of the Suspect Compression Brake Solenoid at the Valve Cover ConnectorNote: In order to troubleshoot a 791-5 diagnostic code, you must use the "Compression Brake Low/High Override" on Cat ET. In order to troubleshoot a 792-5 diagnostic code, you must use the "Compression Brake Med/High Override" on Cat ET.
Turn the keyswitch to the OFF position.
Disconnect the harness at the valve cover connector.
Fabricate a jumper wire in order to create a short between the supply wire for the suspect compression brake solenoid and engine ground.
Turn the keyswitch to the ON position.
Access the diagnostic overrides under the "Diagnostics" menu.
Start the override for the compression brake.
Once Cat ET displays the status of the compression brake solenoid, stop the override.
Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.
Turn the keyswitch to the OFF position. Remove the wire short.Expected Result:A 791-6 diagnostic code or a 792-6 diagnostic code is active at this time.Note: A -5 open circuit diagnostic code will be active for the other compression brake solenoid. Ignore the diagnostic codes for the other compression brake solenoid. Ignore any diagnostic codes for the injector solenoids.Results:
OK - A 791-6 diagnostic code or a 792-6 diagnostic code is active at this time. The harness wiring between the valve cover connector and the ECM is OK. Proceed to Test Step 4.
Not OK - A 791-5 diagnostic code or a 792-5 diagnostic code is active at this time. The ECM did not detect the short at the valve cover connector. There is an open between the valve cover connector and the ECM. Proceed to Test Step 5.Test Step 4. Create a Short Circuit at the Compression Brake SolenoidNote: Two solenoids are activated in order to create a medium br