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| Illustration 1 | g01340975 |
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Connections of the autoshift switch | |
The autoshift switch has two inputs for the ECM. The inputs are Normally Open or Normally Closed. During normal operation, one of the inputs is open and the other input is grounded. A failure is detected when the Normally Open input and the Normally Closed input are in the same state.
This diagnostic code is recorded when the Normally Open input and the Normally Closed input are in the same state.
The possible causes of the problem are listed below:
- There is an Open wire between F849-WH(White) and the ECM.
- There is an Open wire or a grounded wire between F848-OR(Orange) and the ECM.
- There is an Open or a grounded wire between F849-WH(White) and the ECM.
- The switch has failed.
- The ECM has failed. This is unlikely.
Test Step 1. CHECK THE NORMALLY CLOSED CIRCUIT FOR PROPER OPERATION.
- Turn the key start switch and the disconnect switch to the OFF position.
- Disconnect the machine harness from the ECM.
- At machine harness connector J1, measure the resistance from contact J1-44 to contact J2-2.
Expected Result:
With the autoshift switch in the ON position, the resistance should measure more than 5000 ohms. With the autoshift switch in the OFF position, the resistance should measure less than 5 ohms.
Results:
- OK - With the autoshift switch in the ON position, the resistance is more than 5000 ohms. With the autoshift switch in the OFF position, the resistance is less than 5 ohms. Proceed to Test Step 3.
- NOT OK - The switch or the machine harness has failed. Proceed to Test Step 2.
Test Step 2. CHECK THE NORMALLY CLOSED CIRCUIT OF THE SWITCH.
- Disconnect the autoshift switch from the machine harness.
- At the switch, measure the resistance between contact 1 and contact 2. Measure the resistance between contact 3 and contact 2.
Expected Result:
With the autoshift switch in the ON position, the resistance should measure more than 5000 ohms. With the autoshift switch in the OFF position, the resistance should measure less than 5 ohms.
Results:
- OK - With the autoshift switch in the ON position, the resistance is more than 5000 ohms. With the autoshift switch in the OFF position, the resistance is less than 5 ohms.
Repair: The machine harness has failed. Either the Normally Closed circuit (F849-WH(White)) or the return circuit (202-BK(Black)) is open or grounded in the machine harness. Repair the machine harness or replace the machine harness.
STOP
- NOT OK - The switch has failed.
Repair: Replace the autoshift switch. Verify that the new switch corrects the problem.
STOP
Test Step 3. CHECK THE NORMALLY OPEN CIRCUIT FOR PROPER OPERATION.
- At machine harness connector J1, measure the resistance from contact J1-45 (Normally Open contact) to contact J2-2.
Expected Result:
With the autoshift switch in the ON position, the resistance should measure less than 5 ohms. With the autoshift switch in the OFF position, the resistance should measure more than 5000 ohms.
Results:
- OK - With the autoshift switch in the ON position, the resistance is less than 5 ohms. With the autoshift switch in the OFF position, the resistance is more than 5000 ohms. Proceed to Test Step 5.
- NOT OK - The switch or the machine harness has failed. Proceed to Test Step 4.
Test Step 4. CHECK THE NORMALLY OPEN CIRCUIT OF THE SWITCH.
- Disconnect the autoshift switch from the machine harness.
- Measure the resistance between contact 3 and contact 2 at the switch.
Expected Result:
With the autoshift switch in the ON position, the resistance should measure less than 5 ohms. With the autoshift switch in the OFF position, the resistance should measure more than 5000 ohms.
Results:
- OK - With the autoshift switch in the ON position, the resistance should measure less than 5 ohms. With the autoshift switch in the OFF position, the resistance should measure more than 5000 ohms.
Repair: The machine harness has failed. Either the Normally Open circuit (F848-OR(Orange)) or the return circuit (202-BK(Black)) is open or grounded in the machine harness. Repair the machine harness or replace the machine harness.
STOP
- NOT OK -
Repair: The switch has failed. Replace the autoshift switch. Verify that the new switch corrects the problem.
STOP
Test Step 5. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE.
- Clean the contacts of the harness connectors.
- Reconnect all harness connectors.
- Turn the key start switch to the ON position.
- Clear all of the inactive diagnostic codes with the Cat ET.
- Operate the machine.
- Determine if the SPN 1666 - FMI 2 is present.
Expected Result:
SPN 1666 - FMI 2 is present.
Results:
- YES - SPN 1666 - FMI 2 is present.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform the diagnostic code procedure again. If the problem persists, the ECM may have failed. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the cause of the diagnostic code is not found, replace the Transmission ECM. See the Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NO - SPN 1666 - FMI 2 is not present.
Repair: The problem does not exist at this time. The initial problem 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