CP54B, CP56B, CP68B, CP74B, CS54B, CS56B, CS64B, CS66B, CS68B, CS74B, CS76B and CS78B Vibratory Soil Compactors Machine Electronic Control System Caterpillar

Switch Circuits - Test

Usage:

Machine ECM

The following is a list of diagnostic codes (SPN) that are associated with the switch circuits of the machine.

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Table 1
Machine ECM (MID 39)
SPN-FMI	Code Description	System Response
70-2	Parking Brake Switch: Data erratic, intermittent, or incorrect	Disable Propel and Vibe Fault Level - 3

Possible causes for an FMI 2 Diagnostic code are:

The wire is intermittently shorted to the ground circuit while the machine is in operation.
The wire is intermittently shorted to + battery.
An intermittent open circuit exists.
The ECM has failed. ECM failure is unlikely.

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Illustration 1	g03816247
Schematic of the switch circuits

The diagram above is a simplified schematic of the Machine ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown.

For the full Electrical Schematic of the Soil Compactors in this manual, refer to the appropriate media listed below.

For models CS54B and CP54B refer to Electrical Schematic, UENR6386.
For models CS56B, CP56B, CS64B, CS66B, CS68B and CP68B refer to Electrical Schematic, UENR6388.
For models CS74B, CP74B, CS76B and CS78B refer to Electrical Schematic, UENR6384.

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Table 2
Contacts Closed states of the "Park Brake Switch"
Switch Position	Brake Function	LED Indicator
ON	2 & 3	5 & 6
OFF	2 & 1	5 & 4

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.

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

FMI 2 diagnostic code, proceed to Table 3.

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Table 3
FMI 2 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check The Harness A. Turn the disconnect switch and the key start switch OFF. B. Inspect all harness connections. Make sure that the connectors are clean and tight. C. Check the connectors for proper mating. Ensure that all the seals are present and in place. D. Check the harness for signs of damage or abrasion. E. Check the wires at the connector. Ensure that the wires are secured tightly into the connector. Take care not to pull the wire out of the connector. F. Check the exposed wires at the connectors for nicks or signs of abrasion. G. Check for moisture inside the connector.	The machine harness connectors are tight and free of corrosion.	OK - The machine harness connectors are tight and free of corrosion. Proceed to Test Step 2. NOT OK - The machine harness connectors are in need of repair. Repair: Repair or replace the machine harness. Proceed to Test Step 3.
2. Check The Harness For An Open A. Turn the key start switch and the disconnect switch to the OFF position. B. Disconnect the machine harness connector from the switch. C. Disconnect the machine harness connectors from the ECM. D. At the harness connector for the switch, place a jumper wire between the normally open (N/O) contact and the normally closed (N/C) contact. E. At machine harness connector for the ECM, measure the resistance between the normally open (N/O) contact and the normally closed (N/C) contact.	The resistance is less than 5 Ω.	OK - The resistance is less than 5 Ω. The (N/O) and (N/C) circuits are not open in the machine harness. Proceed to Test Step 3. NOT OK - The resistance reading for the (N/O) and (N/C) circuits greater than 5K Ω. There is an open in one of the circuits. 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 4.
3. Check The Switch A. The disconnect switch and the key start switch remain in the OFF position. B. Remove the switch from the machine harness. C. Measure the resistance between the normally open contact and the switch return or ground. Toggle the operation of the switch and observe resistance changes. D. Measure the resistance between the normally closed contact and the switch return or ground. Toggle the operation of the switch and observe resistance changes.	Open resistance is greater than 5K Ω. Closed resistance is less than 5 Ω.	OK - The measurements are correct. Proceed to Test Step 4. NOT OK - One or more of the measurements was incorrect. 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. Repair: Replace the switch. Proceed to Test Step 4.
4. Check If The Diagnostic Code Remains A. Reconnect all harness connectors. Return machine to normal operating condition. B. Turn the key start switch and the disconnect switch ON. C. Clear all diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock. F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, 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 effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.