844K Wheel Dozer Caterpillar

Operator Control Switch (Switch to Ground) - Test

Usage:

844K K4Y

Transmission ECM

The following is a list of codes associated with the switch circuits for the Transmission ECM

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Table 1
Transmission ECM (MID 81)
DTC	Code Description	System Response
70-2	Parking Brake Switch: Data Erratic, Intermittent, Or Incorrect	Parking brake will not disengage when requested.
348-3	Transmission Lockout Switch: Voltage Above Normal	When this diagnostic code occurs, there is no change in the system operation. The transmission will remain in the last known state, either locked or unlocked.
348-4	Transmission Lockout Switch: Voltage Below Normal	When this diagnostic code occurs, there is no change in the system operation. The transmission will remain in the last known state, either locked or unlocked.
626-3	Steering/Transmission Lock Switch : Voltage Above Normal	When this diagnostic code occurs, there is no change in the system operation. The transmission will remain operational, even if the mechanical steering lock is in the locked position.
626-4	Steering/Transmission Lock Switch: Voltage Below Normal	When this diagnostic code occurs, there is no change in the system operation. The transmission will remain operational, even if the mechanical steering lock is in the locked position.
2678-3	Access Platform Position Switch: Voltage Above Normal (AKA - Stairway Position Switch)	When this code is active, the driver will be unable to shift the machine out of the neutral position.
2678-4	Access Platform Position Switch: Voltage Below Normal (AKA - Stairway Position Switch)	When this code is active, the driver will be unable to shift the machine out of the neutral position.
3797-3	Operator Seat Belt Switch: Voltage Above Normal	The operator will be unable to start the machine.
3797-4	Operator Seat Belt Switch: Voltage Below Normal	The operator will be unable to start the machine.

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 Transmission ECM is unlikely.

Possible Causes for an FMI 3 Diagnostic code are:

The ground wire is open.
A signal is permanently open.
The switch has failed.
The ECM has failed. A failure of the Transmission ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

A short to ground.
The switch has failed.
The ECM has failed. A failure of the Transmission ECM is unlikely.

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Illustration 1	g03647544
Schematic of the Transmission ECM J1 Operator Control Switch (Switch to Ground) Connections

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Illustration 2	g03651287
Schematic of the Transmission ECM J2 Operator Control Switch (Switch to Ground) Connections

Note: The diagram above is a simplified schematic 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, UENR4996, "844K Wheel Dozer (T4F) Electrical System Schematic" for the complete schematic.Electrical Schematic, UENR1697, "844K Wheel Dozer (LRC) Electrical System Schematic" for the complete schematic.

Use the table below to aid in the troubleshooting of the suspect faulty switches. The tables display the expected continuity for the switches for the given switch states.

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Table 2
Status of the Parking Brake Switch
Contacts	Switch State	Continuity
1, 2	Engaged	No
1, 2	Disengaged	Yes
2, 3	Engaged	Yes
2, 3	Disengaged	No
4, 5	Engaged	No
4, 5	Disengaged	Yes
5, 6	Engaged	Yes
5, 6	Disengaged	No

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Table 3
Status of the Transmission Lockout Switch
Switch Position	T908-BU Circuit N/O J2-47	T909-YL Circuit N/C J2-44
Locked	Closed	Open
Unlocked	Open	Closed

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Table 4
Status of the Steering/Transmission Lock Switch
Switch Position	G748-PU Circuit N/O J2-34	G749-YL Circuit N/C J2-33
Locked	Closed	Open
Unlocked	Open	Closed

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Table 5
Status Ladder Position Switch
Ladder Extended	M904-OR Circuit N/O J2-31	M905-WH Circuit N/C J2-59
Ladder Retracted	Open ⁽¹⁾	Closed ⁽²⁾
"Ladder Position" Switch	Open	Closed

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^( 1 )	Open to return contact 299-BK (ground)
^( 2 )	Closed to return contact 299-BK (ground)

Implement ECM

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Table 6
Implement ECM (MID 82)
DTC	Code Description	System Response
490-3	Implement Lockout Switch: Voltage Above Normal	Activates when both pins are open. When this diagnostic code occurs, there is no change in the system operation. The Implement system will remain in the last known state, either "locked" or "unlocked."
490-4	Implement Lockout Switch: Voltage Below Normal	Activates when both pins are grounded. When this diagnostic code occurs, there is no change in the system operation. The Implement system will remain in the last known state, either "locked" or "unlocked."
3999-3	Right Joystick Trigger Switch: Voltage Above Normal	Loss of trigger functionality. Refer to: Systems Operation Testing and Adjusting , UENR4599, "844K Wheel Dozer (T4F and LRC) " for switch operation information.
3999-4	Right Joystick Trigger Switch: Voltage Below Normal	Activates when both pins are grounded.

Possible Causes for an FMI 3 Diagnostic code are:

The ground wire is open.
A signal is permanently open.
The switch has failed.
The ECM has failed. A failure of the Transmission ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

A short to ground.
The switch has failed.
The ECM has failed. A failure of the Transmission ECM is unlikely.

Use the tables below to aid in the troubleshooting of the suspect faulty switches. The tables display the expected continuity for the switches for the given switch states.

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Illustration 3	g03651258
Schematic of the Implement ECM J1 Operator Control Switch (Switch to Ground) Connections

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Table 7
Status of Implement Lockout Switch
Implement Lockout Switch	(N/O) Contacts	Open
ON	Closed	Open
OFF	Open	Closed

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Table 8
Status of the Joystick Prophet Handle Trigger Push Button
Trigger Switch Condition	(N/O) Contacts	(N/C) Contacts
Trigger Released (Dual Tilt Mode)	Open	Closed
Trigger Depressed (Single Tilt Mode)	Closed	Open

Diagnostic Trouble Code Procedure

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. Check the wiring for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing a troubleshooting procedure.

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Table 9
Troubleshooting Test Steps	Values	Results
1. Identify The Active FMI Code Associated With The Sensor Circuit	Code present.	FMI 2 diagnostic code, proceed to Test Step 2. FMI 3 diagnostic code, proceed to Test Step 4. FMI 4 diagnostic code, proceed to Test Step 9.
Begin Process For FMI 2 Troubleshooting HERE
2. Check The Circuit For A Short A. Turn the key switch OFF. B. Disconnect the switch from the machine harness. C. Disconnect the J1 and J2 machine harness connections from the ECM. D. At the machine harness connector for the ECM, measure the resistance between each signal contact and every contact for the J1 and J2 harness connectors.	The resistance is greater than 5K Ω.	OK - The resistance is correct. Proceed to Test Step 3. NOT OK - The resistance check is not correct. Repair: There is a short in the signal circuits of the machine harness. Repair or replace the machine harness. STOP
3. Check the Operation of the Switch. A. The key switch remains OFF. B. Reconnect all harness connectors. C. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation.	The switch operates correctly.	OK - The switch is operating correctly. Proceed to Test Step 12. NOT OK - The switch is not operating correctly. The switch has failed. Repair: Replace the switch. STOP
Begin Process For FMI 3 Troubleshooting HERE
4. Check the Harness For an Open A. Turn key start switch and disconnect switch OFF. B. Disconnect the switch from the machine harness. C. Disconnect the J1 and J2 machine harness connectors at the ECM. D. At the machine harness connector for the switch, place a jumper between the two signal wires at the switch connector. Check for low resistance at the ECM connector. E. At the machine harness connect for the ECM, measure the resistance between the signal contact and frame ground.	The resistance is less than 5 Ω.	OK - The circuit is correct. Proceed to Test Step 5. NOT OK - The resistance is greater than 5K Ω. The circuit is open. Repair: Repair or replace the machine harness. Note: A resistance that is greater than 5 Ω but less than 5K Ω indicates a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω indicates an open in the circuit. STOP
5. Check the Harness for a Short A. The key switch remains OFF. B. All harness connectors remain disconnected. C. Remove the jumper wire installed in the previous step. D. At the machine harness connector for the ECM, measure resistance between the signal contacts and all other contacts of the J1 and J2 harness connectors.	The resistances are greater than 5K Ω.	OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 6. NOT OK - The resistance less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the wire with the low resistance reading. Repair or replace the machine harness. Note: A resistance that is greater than 5 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. STOP
6. Check the Ground Source for the Switch. A. The key switch remains OFF. B. All harness connectors remain disconnected. C. At the switch, measure resistance between the ground contact and frame ground.	The resistance is less than 5 Ω.	OK - The resistance is less than 5 Ω. Proceed to Test Step 7. NOT OK - The resistance is greater than 5K Ω. Repair: The switch does not have a good ground source. Replace the harness between the switch and the ground source. Note: A resistance that is greater than 5 ohms but less than 5K ohms indicates a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms indicates an open in the circuit. STOP
7. Check the Operation of the ECM. A. The key switch remains OFF. B. Reconnect all harness connections. C. Using a wire removal tool, remove the signal wires and socket from the machine harness connector to the switch. D. Turn the key switch ON. E. Use a multimeter probe to contact both signal wire pins through the empty space in the harness connector. F. Ground the other end of the multimeter probe to frame ground. G. Observe the status of the diagnostic code.	The FMI 3 changes to an FMI 4.	OK - The ECM is operating correctly. Proceed to Test Step 8. NOT OK - The FMI 3 remains active. The ECM may have failed. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "ECM - Replace" STOP
8. Check the Operation of the Switch. A. Turn the key switch OFF. B. Reinstall the signal wire removed in the previous step. C. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation.	The switch operates correctly.	OK - The switch is operating correctly. Proceed to Test Step 12. NOT OK - The switch is not operating correctly. The switch has failed. Repair: Replace the switch. STOP
Begin Process For FMI 4 Troubleshooting HERE
9. Check The Switch A. Turn the key switch and disconnect switch OFF. B. Unplug the switch from the machine harness. C. Turn the key switch and disconnect switch ON. D. Observe the status of the diagnostic code.	The FMI 4 diagnostic code remains active.	OK - The FMI 4 diagnostic code remains active. Proceed to Test Step 10. NOT OK - The FMI 4 changes to an FMI 3. The switch has failed. Repair: Replace the switch. Verity that the new switch corrects the diagnostic code. STOP
10. Check the Harness for a Short A. The turn the key start switch and disconnect switch OFF. B. Unplug the J1 and J2 machine harness connectors from the ECM. C. At the machine harness connector for the ECM, measure resistance between the signal contact and all other contacts of the J1 and J2 harness connectors.	The resistances are greater than 5K ohms.	OK - The resistance is greater than 5K ohms. The harness circuit is correct. Proceed to Test Step 11. NOT OK - The resistance less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the wire with the low resistance reading. Repair or replace the machine harness. Note: A resistance that is greater than 5 ohms but less than 5K ohms would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K ohms would indicate an open in the circuit. STOP
11. Check the Operation of the Switch. A. The key start switch and disconnect switch remain OFF. B. Check the operation of the switch. Refer to the table for the suspected faulty switch at the beginning of this procedure for switch operation.	The switch operates correctly.	OK - The switch is operating correctly. Proceed to Test Step 12. NOT OK - The switch is not operating correctly. The switch has failed. Repair: Replace the switch. STOP
12. Check If The Diagnostic Code Remains A. Inspect the harness connectors and clean the contacts of the harness connectors. B. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit. C. Reconnect all harness connectors. D. Turn key start switch and disconnect switch ON. E. Operate the machine. F. Check the status of the diagnostic code.	The diagnostic code is not active.	OK - The diagnostic code is still active. Repair: Check the status of the diagnostic code. If the cause of the problem is not found, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "ECM - Replace". STOP NOT OK - The continuity check is not correct. Repair: There is an open in the signal circuits of the machine harness. Repair or replace the machine harness. STOP