Conditions Which Generate This Code:
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| Illustration 1 | g01389548 |
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Compression Brake Switch connections | |
The compression brake switch is equipped on the 24M Motor Grader.
The compression brake switch is a two-pole, double-throw switch. One pole is used to provide two switch to ground inputs to the ECM to indicate the status of the switch. The other pole of the switch is not used for operation of the ECM.
During normal operation, one of the inputs is not connected to ground and the other input is connected to ground through the switch contacts. An internal pull-up voltage is present at the ECM switch inputs. When the input is grounded through the switch, the ECM detects the ground signal.
The FMI 03 diagnostic code is activated by the ECM when neither of the inputs is showing a ground signal.
The conditions that could cause the ECM to activate this diagnostic code are listed below:
- The switch has failed.
- The common ground circuit is open or has a bad connection.
- There is an open or a bad connection in one or both of the switch input circuits.
- The ECM has failed. This situation is unlikely.
Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, that all connections are secure, and that all connections are in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.
Note: The following test procedure may cause other diagnostic codes to be activated. Ignore these created diagnostic codes and clear the diagnostic codes when the problem has been corrected.
Test Step 1. CHECK THE SWITCH
| Contact States of the Compression Brake Switch | ||
| Switch Position | Input J2-60 (wire E717-GN(Green)) | Input J2-61 (wire E716-GY(Grey)) |
| Compression Brake ON | Open(1) | Closed(2) |
| Compression Brake OFF | Closed | Open |
| (1) | Open to common ground circuit A202-BK. |
| (2) | Closed to common ground circuit A202-BK. |
- Turn the switch key and the disconnect switch to the OFF position.
- Disconnect the machine harness connector from the switch.
- With the switch in the ON position, measure the resistance from switch common contact 2 to switch input contact 1. Compare the measurement to the switch contact status table above.
- With the switch in the ON position, measure the resistance from switch common contact 2 to switch input contact 3. Compare the measurement to the switch contact status table above.
- Move the switch to the OFF position and repeat Steps "C" and "D".
Expected Result:
The resistance measurements in each switch position are correct according to the switch contact status table at the beginning of this test step.
Results:
- YES - All of the resistance checks for the switch are correct in each switch position according to the contact status table. The switch is working correctly. Proceed to Test Step 2.
- NO - The switch states do not match the table. The switch has failed.
Repair: Replace the compression brake switch. After the switch is replaced, verify that the switch operation is correct before operating the machine.
STOP
Test Step 2. CHECK SWITCH COMMON GROUND CIRCUIT FOR AN OPEN
The switch key and the disconnect switch remain in the OFF position. The machine harness remains disconnected from the switch.
- At the machine harness connector for the switch, measure the resistance from switch common ground contact 2 (wire A202-BK(Black)) to frame ground.
- While observing the multimeter resistance measurement, wiggle the machine harness connector of the switch. Gently pull on the wires and move the wires from side to side.
Expected Result:
The resistance measurement is less than 5 ohms at all times during the manipulation of the harness.
Results:
- OK - The resistance measurement is less than 5 ohms. The switch common ground circuit is correct. Proceed to Test Step 3.
- NOT OK - The resistance measurement is greater than 5 ohms. There is an open or a bad connection in the switch common ground circuit (wire A202-BK(Black)).
Repair: A resistance measurement that is greater than 5000 ohms could indicate that a wire is either not connected or is open. A resistance measurement that is greater than 5 ohms but less than 5000 ohms could indicate that one of the connection points or splice connections in the ground circuit is not open but is not a good connection.
Refer to the complete machine Electrical System Schematic. Check all the connectors that are in the ground circuit starting from the switch and working your way back to the rear cab ground terminal connections. Ensure that all connections are clean, that all connections are secure, and that all connections are in good condition. Repair the machine harness or replace the machine harness.
STOP
Test Step 3. CHECK THE SWITCH INPUT CIRCUITS FOR AN OPEN
The switch key and the disconnect switch remain in the OFF position. The machine harness remains disconnected from the switch.
- At the machine harness connector for the switch, place a jumper wire between input contact 1 (wire E717-GN(Green)) and input contact 3 (wire E716-GY(Grey)).
- Disconnect the machine harness connectors J1 and J2 from the ECM.
- At the machine harness ECM connector J2, measure the resistance from switch input contact J2-60 (wire E717-GN(Green)) to switch input contact J2-61 (wire E716-GY(Grey)).
- While observing the multimeter resistance measurement, wiggle the machine harness connectors for the ECM. Gently pull on the wires and move the wires from side to side.
- While observing the multimeter resistance measurement, wiggle the machine harness connector of the switch. Gently pull on the wires and move the wires from side to side. Do not disconnect the jumper wire.
Expected Result:
The resistance measurement is less than 5 ohms at all times during the manipulation of the harness.
Results:
- OK - The resistance measurement is less than 5 ohms. The switch inputs circuits are not open within the machine harness. Proceed to Test Step 4.
- NOT OK - The resistance measurement is greater than 5 ohms. There is a problem with one or both of the switch input circuits in the machine harness.
Repair: Refer to the connection diagram illustration at the beginning of this procedure.
Connect one end of the jumper wire to the switch harness connector common ground contact 2 (wire A202-BK(Black).
One at a time, connect the other end of the jumper wire to each switch input and check the resistance at the ECM harness connector J1 from the appropriate input contact to one of the ground contacts (wire A202-BK(Black)) that are used on the J1 connector. This will identify the input circuit that is open or has the bad connection.
A resistance measurement that is greater than 5000 ohms could indicate that a wire is either not connected or is open. A resistance measurement that is greater 5 ohms but less than 5000 ohms could indicate that one of the connection points in the circuit is not open but is not a good connection.
Refer to the complete machine Electrical System Schematic. Check all the connectors that are in the suspect input circuit. Ensure that all connections are clean, that all connections are secure, and that all connections are in good condition. Repair the machine harness or replace the machine harness.
STOP
Test Step 4. CHECK THE STATUS OF THE DIAGNOSTIC CODE
- Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that is caused by excessive heat, corrosion, or chafing.
- Perform a
45 N (10 lb) pull test on each of the wires that are associated with the sensor circuit. - Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the machine.
- Check the status of the CID 2734 FMI 03 diagnostic code.
Expected Result:
The CID 2734 FMI 03 diagnostic code is active.
Results:
- YES - The CID 2734 FMI 03 diagnostic code is active. The diagnostic code has not been corrected.
Repair: Check the input circuits of the switch again. Use the AVSpare Electronic Technician (ET) service tool, if available, to perform a wiggle test on the machine wiring harness. The wiggle test can detect a momentary short circuit or detect an intermittent short circuit. A wiggle test can also be used to detect open points in the machine wiring harness.
If the cause can not be found, the ECM may have failed. Verify that all possible causes of the diagnostic code have been investigated before replacement of the ECM.
Prior to replacing an ECM, always contact your dealership's Technical Communicator for possible consultation with AVSpare. This consultation may greatly reduce repair time. If the cause of the diagnostic code is not found, replace the ECM. Refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NO - The CID 2734 FMI 03 is not active. The diagnostic code does not exist at this time.
Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.
STOP