0312675 JOHNSON SCREEN,Filter

Table 1
Diagnostic Codes Table
Code and Description Conditions which Generate this Code System Response
1248-5 Retarder Solenoid current below normal The Electronic Control Module (ECM) detects a current flow that is below normal. The code is logged.
The exhaust brake relay can not be actuated.
1248-6 Retarder Solenoid current above normal The ECM detects a current flow that is above normal. The code is logged.
The exhaust brake relay can not be actuated. Note: Although the -5 and -6 diagnostic codes refer to a retarder solenoid, the detected fault is for the relay circuit.An exhaust brake is an auxiliary braking device which is designed to decrease engine speed. The device restricts the flow of exhaust gas which creates back pressure to the pistons and results in rapid deceleration. The ECM controls the exhaust brake through a relay. This relay controls a solenoid valve which actuates the exhaust brake.Note: Program the "Exhaust Valve Actuation System Instation Status" to "Installed" if an exhaust brake is installed. There are two modes of operation for the exhaust brake . The two modes are "Vehicle Brake" and "Overspeed Protection". These modes of operation are selectable via a switch input to the ECM. Both modes of operation have programmable parameters. Information on the default settings and ranges for "Exhaust Offset Speed" and "Exhaust Over Speed Trip" can be found in Troubleshooting, "Configuration Parameters".Close the switch input for the exhaust brake in order to select the "Vehicle Brake Mode". The status for the "Exhaust Brake Switch" will show the number 4 for "Vehicle Brake Mode".Open the switch input for the exhaust brake in order to select the "Overspeed Protection Mode". The status for the "Exhaust Brake Switch" will show the number 0 for "Overspeed Protection Mode".The "Vehicle Brake Mode" will activate when all of the following conditions are met:
The switch input for the exhaust brake is closed.
Engine speed is greater than the sum of the desired speed and the programmed "Exhaust Offset Speed".
Desired engine speed is low idle.
The fuel position is less than two cubic millimeters.The "Vehicle Brake Mode" will not activate when any of the following conditions are met:
The keyswitch is in the OFF position.
Remote Shutdown has been activated.
The engine monitoring system shut down the engine.
A 1248-05 diagnostic code is active.
A 1248-06 diagnostic code is active.The "Overspeed Protection Mode" will activate when all of the following conditions are met:
The switch input for the exhaust brake is open.
The engine speed is greater than the programmed "Exhaust Over Speed Trip".
The fuel position is less than two cubic millimeters.The "Overspeed Protection Mode" will not activate when any of the following conditions are met:
The keyswitch is in the OFF position.
Remote Shutdown has been activated.
The engine monitoring system shut down the engine.
A 1248-05 diagnostic code is active.
A 1248-06 diagnostic code is active.The "Diagnostic Overides" screen on the Caterpillar Electronic Technician (ET) allows the technician to activate the exhaust brake.
Illustration 1 g01415879
Schematic of the circuit for the exhaust brake
The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove electrical power from the ECM.
Illustration 2 g01388291
Engine view (typical example)
(1) J1/P1 ECM connectors
Thoroughly inspect the ECM connector J1/P1. Also, inspect all wire terminations in the circuit. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".
Illustration 3 g01308302
P1 terminals of the circuit for the exhaust brake relay
(P1-05) Digital sensor return
(P1-13) Exhaust brake driver
(P1-40) Exhaust brake switch
(P1-67) Driver return for the exhaust brake
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit for the exhaust brake.
Check the allen head screw on each ECM connector for the proper torque. Also check the allen head screw on the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points from the ether injection solenoid 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 and of pinch points.Results:
OK - The connectors and wiring appear to be OK. Proceed to Test Step 2.
Not OK - The connectors and/or wiring are not OK.Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Verify that the problem is resolved.STOPTest Step 2. Verify the Desired Mode of Operation for the Exhaust BrakeNote: The system for the exhaust brake can appear to be failed if the input switch circuit for the exhaust brake is failed.
Restore electrical power to the ECM.
Use Cat ET in order to connect to the ECM.
Operate the switch and monitor the status for the "Exhaust Brake Switch". Expected Result: The status for the "Exhaust Brake Switch" changes from the number 4 to the number 0 state.Results:
OK - The "Exhaust Brake Switch" is operating correctly. Proceed to Test Step 7.
Not OK - There is a problem in the circuit for the "Exhaust Brake Switch". Proceed to Test Step 3.Test Step 3. Short the Wires at the Switch for the Exhaust Brake
Remove the wire for the digital sensor return from terminal 1 of the switch.
Restore electrical power to the engine ECM.
Check the status of the "Exhaust Brake Switch" on Cat ET.
Short the wire for the digital sensor return to terminal 2 of the switch.
Check the status of the "Exhaust Brake Switch" on Cat ET. Expected Result: The status for the "Exhaust Brake Switch" is the number 0 when the wire is removed. The status for the "Exhaust Brake Switch" is the number 4 when the digital return wire is shorted to terminal 2 of the switch.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 Step 4.Test Step 4. Check for an Open in