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| Illustration 1 | g01283808 |
Schematic of the Armbar/Seat Switches Circuit | |
This diagnostic code is associated with the Armbar/Seat Switches. These switches are connected to two inputs of the the ECM. One contact is normally open. The other contact is normally closed. Wire G984-PK is closed and wire G985-PU is open, when the Armbar is in the UP position. Wire G984-PK is open and wire G985-PU is closed, when the Armbar is in the DOWN position AND the Seat is OCCUPIED. If the Armbar is in the DOWN position and the Seat is UNOCCUPIED, BOTH circuits will be open. Refer to Table 1.
| Status of the Armbar/Seat Switch Circuit | |||
| Armbar Position | Seat Status | G984-PK Circuit J1-33 |
G985-PU Circuit J2-58 |
| Up | N/A | Closed | Open |
| Down | Unoccupied | Open | Open |
| Down | Occupied | Open | Closed |
An FMI 04 diagnostic code is recorded when the status of both the inputs are grounded.
The possible causes of this diagnostic code are listed below:
- The "NORMALLY CLOSED" signal circuit (wire G984-PK) is shorted to ground.
- The "NORMALLY OPEN" signal circuit (wire G985-PU) is shorted to ground.
- The Armbar Switch has failed.
- The Seat Switch has failed.
- The ECM has failed. This is unlikely.
System Response:
The machine will be brought to a controlled stop. The park brake will be engaged. The implements will be locked out.
Test Step 1. CHECK THE SWITCHES
- Disconnect the negative battery cable and turn the key start switch to the OFF position.
- Disconnect the Armbar switch and the Seat switch from the machine harness.
- Connect one lead from a multimeter to contact A (wire 203-BK) of the connector for the Armbar switch.
- Connect the other lead from a multimeter to contact B (wire G983-GN) of the connector for the Armbar switch.
- Put the Armbar in the UP position.
- Measure the resistance between contact A (wire 203-BK) and contact B (wire G983-GN). Note the resistance.
- Put the Armbar in the DOWN position.
- Measure the resistance between contact A (wire 203-BK) and contact B (wire G983-GN). Note the resistance.
- Disconnect the lead from contact B (wire G983-GN) and connect the lead to contact C (wire G984-PK). Note the resistance.
- Measure the resistance between contact A (wire 203-BK) and contact C (wire G984-PK). Note the resistance.
- Put the Armbar in the UP position.
- Measure the resistance between contact A (wire 203-BK) and contact C (wire G984-PK). Note the resistance.
- Connect one lead from a multimeter to contact 1 (wire G983-GN) of the connector for the Seat switch.
- Connect the other lead from a multimeter to contact 2 (wire G985-PU) of the connector for the Seat switch.
- The Seat is UNOCCUPIED.
- Measure the resistance between contact 1 (wire G983-GN) and contact 2 (wire G985-PU). Note the resistance.
- Occupy the Seat.
- Measure the resistance between contact 1 (wire G983-GN) and contact 2 (wire G985-PU). Note the resistance.
Expected Result:
The resistances agree with Table 1.
The resistance from Armbar Switch contact A to contact B is greater than 5000 ohms when the Armbar is UP, and the resistance from contact A to contact B is less than 5 ohms when the Armbar is DOWN.
The resistance from Armbar Switch contact A to contact C is less than 5 ohms when the Armbar is UP, and the resistance from contact A to contact C is greater than 5000 ohms when the Armbar is DOWN.
The resistance from Seat Switch contact 1 to contact 2 is greater than 5000 ohms when the Seat is UNOCCUPIED, and the resistance from Seat Switch contact 1 to contact 2 is less than 5 ohms when the Seat is OCCUPIED.
Results:
- YES - The resistance from Armbar Switch contact A to contact B is greater than 5000 ohms when the Armbar is UP, and the resistance from Armbar Switch contact A to contact B is less than 5 ohms when the Armbar is DOWN. The resistance from Armbar Switch contact A to contact C is less than 5 ohms when the Armbar is UP, and the resistance from Armbar Switch contact A to contact C is greater than 5000 ohms when the Armbar is DOWN. The resistance from Seat Switch contact 1 to contact 2 is greater than 5000 ohms when the Seat is UNOCCUPIED, and the resistance from Seat Switch contact 1 to contact 2 is less than 5 ohms when the Seat is OCCUPIED. Proceed to Test Step 2.
- NO - There are incorrect resistance readings. The switch with the incorrect resistance reading has failed.
Repair: Replace the switch.
STOP
Test Step 2. CHECK THE SIGNAL CIRCUITS FOR A SHORT TO GROUND
- The key start switch remains in the OFF position.
- The Armbar switch and the Seat switch remain disconnected from the machine harness.
- Disconnect the machine harness connectors from the ECM.
- At the harness connector for the ECM, measure the resistance between contact J1-33 (wire G984-PK) and frame ground.
- Measure the resistance between contact J2-58 (wire G985-PU) and frame ground.
Expected Result:
The resistances should be greater than 5000 ohms.
Results:
- OK - The resistances are greater than 5000 ohms.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NOT OK - The resistance is less than 5000 ohms on any of the readings.
Repair: The circuit with the low resistance is shorted in the machine harness. Repair the machine harness or replace the machine harness.
STOP