HOUSING AS 9T8070 - Caterpillar

Transmission ECM
Table 1
Transmission ECM (MID 81)
DTC Code Description System Response
1834-2 Ignition Key Switch : Data Erratic, Intermittent, Or Incorrect Operator is unable to start the machine. DTC Root Causes and Schematics
Possible Causes for an FMI 2 Diagnostic code are:
A short circuit exists.
An open circuit exists.
The switch has failed.
The ECM has failed. A failure of the ECM is unlikely.
Illustration 1 g03505707
Transmission ECM wiring connection for Key Start switch.
Note: The diagrams above are simplified schematics of the ECM switch connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, RENR3118 for the complete schematic.Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear the diagnostic trouble codes when the original diagnostic trouble code has been corrected. Troubleshooting Process
Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure.
Table 2
Troubleshooting Test Steps Values Results
Begin Process For FMI 2 Troubleshooting HERE
1. Check The Switch
A. Turn the disconnect switch and the key start switch OFF.
B. Disconnect the switch from the machine harness.
C. Measure the resistance between the return or ground pin and all input pins, one at a time.
D. Move the switch through the range of selections, and verify continuity.
The resistance should be less than 5 Ω when switch operation indicates continuity, and greater than 5K Ω when switch operation indicates no continuity. OK: The resistance is as expected.
Proceed to Test Step 2.
NOT OK: The resistance is not as expected.
Repair: Replace the switch. Verify that the new switch resolves the diagnostic code.
Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the switch. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.
STOP
2. Check The Circuit For An Open
A. Turn the disconnect switch and the key start switch OFF.
B. Disconnect the switch and ECM from the machine harness.
C. Use a jumper wire between each contact on the machine harness at the switch end, one at a time.
D. Measure the resistance at the corresponding ECM harness pins.
The resistance is less than 5 Ω. OK: The resistance is less than 5 Ω.
Proceed to Test Step 3.
NOT OK: The resistance is greater than 5K Ω.
Repair: The circuit wire is open in the machine harness. Repair or replace the machine harness.
Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit.
STOP
3. Check The Harness
A. The disconnect switch