D7E Track-Type Tractor Power Train Systems Caterpillar

Switch Circuits - Test

Usage:

D7E MDB

Machine ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the switch circuits of the machine.

Show/hide table

Table 1
Machine ECM
DTC	Code Description	System Response
70-3	Parking Brake Switch: Voltage Above Normal	A Warning Level 1 Will Be Generated.
70-4	Parking Brake Switch: Voltage Below Normal	A Warning Level 1 Will Be Generated.

Possible causes for an FMI 3 Diagnostic code are:

The switch has failed.
The common ground circuit is an open connection or the circuit 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. ECM failure is unlikely.

Possible causes for an FMI 4 diagnostic code are:

The switch has failed.
There is a short to a ground source in one or both of the switch input circuits
The ECM has failed. ECM failure is unlikely.

Show/hide table




Illustration 1	g03696778
Schematic of the switch circuits

Note: The diagram above is a simplified schematic of the Machine ECM and the Switch Circuit connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR4073 for the complete schematic.

Show/hide table

Table 2
Contact states of the "Parking Brake Operator Switch"
Switch Position	OFF Input J1-35 wire 419-YL(Yellow)	ON Input J1-40 wire F780-PK(Pink)
Parking Brake ON	Closed⁽¹⁾	Open⁽²⁾
Parking Brake OFF	Open	Closed

Show/hide table

⁽¹⁾	Closed to ground circuit L740--BR(Brown).
⁽²⁾	Open to ground circuit L740--BR(Brown).

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.

1. Identify the active FMI code associated with the components.
2. Determine which code is present and use the list below to determine which procedure to follow.

FMI 3 DTC, proceed to Table

FMI 4 DTC, proceed to Table

Show/hide table

Table 3
Begin Process For FMI 3 Troubleshooting HERE
Troubleshooting Test Steps	Values	Results
1. 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 2. 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. Proceed to Test Step 5.
2. Check The Circuit For A Short A. The disconnect switch and the key start switch remain in the OFF position. B. At the machine harness connector for the ECM measure the resistance between the signal circuits and every other contact in the wiring harness.	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 circuit of the machine harness. Repair or replace the machine harness. Proceed to Test Step 5.
3. Check The Switch A. Measure the resistance from the normally open contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes. B. Measure the resistance from the normally closed contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes.	Open resistance should be greater than 5k Ω. Closed resistance should be less than 5 Ω.	OK - The measurements are correct. Proceed to Test Step 4. NOT OK - One or more of the measurements was incorrect. Repair: Replace the switch. Verity that the new switch corrects 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 circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. Proceed to Test Step 5.
4. Check The Signal Circuits For An Open A. Reconnect the switch to the machine harness. B. Perform Test Step 4 AGAIN, HOWEVER instead of measuring resistance from switch contacts, measure from the corresponding contacts on the ECM harness.	Open resistance should be greater than 5k Ω. Closed resistance should be less than 5 Ω.	OK - The measurements are correct. Proceed to Test Step 5. NOT OK - One or more of the measurements was incorrect. Repair: 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. Proceed to Test Step 5.
5. 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. B. Reconnect all harness connectors. C. Turn key start switch and disconnect switch ON. D. Operate the machine. 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 circuit of the machine harness. Repair or replace the machine harness. STOP

Show/hide table

Table 4
Begin Process For FMI 4 Troubleshooting HERE
Troubleshooting Test Steps	Values	Results
1. Check The Switch A. Measure the resistance from the normally open contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes. B. Measure the resistance from the normally closed contact to the switch return or ground. Toggle the operation of the switch and observe resistance changes.	Open resistance should be greater than 5k Ω. Closed resistance should be less than 5 Ω.	OK - The measurements are correct. Proceed to Test Step 2. NOT OK - One or more of the measurements was incorrect. Repair: Replace the switch. Verity that the new switch corrects 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 circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. Proceed to Test Step 8.
2. Check The Signal Circuits For An Open A. Reconnect the switch to the machine harness. B. Perform Test Step 4 AGAIN, HOWEVER instead of measuring resistance from the switch contacts, measure from the corresponding contacts on the ECM harness.	Open resistance should be greater than 5k Ω. Closed resistance should be less than 5 Ω.	OK - The measurements are correct. Proceed to Test Step 3. NOT OK - One or more of the measurements was incorrect. Repair: 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. Proceed to Test Step 3.
3. 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. B. Reconnect all harness connectors. C. Turn key start switch and disconnect switch ON. D. Operate the machine. 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 circuit of the machine harness. Repair or replace the machine harness. STOP