SENSOR GP-PRESSURE 6V1944 - Caterpillar

A relay is a component that uses a small amount of electrical current to control the state of a circuit. The circuit is either opened or closed. Possible causes for an FMI 5 diagnostic code are:
The supply circuit is open.
The return circuit is open.
The relay has failed.
The ECM has failed. A failure of the ECM is unlikely.Possible causes for an FMI 6 diagnostic code are:
A short to ground exists.
The relay has failed.
The ECM has failed. A failure of the ECM is unlikely.
Illustration 1 g03817506
Schematic of the relay circuits
Note: 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.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 harness 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 the 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 5 diagnostic code, proceed to Table 2.
FMI 6 diagnostic code, proceed to Table 3.
Table 2
FMI 5 Troubleshooting
Troubleshooting Test Steps Values Results
1. Check The Relay
A. Turn the key start switch and disconnect switch OFF.
B. Disconnect the relay from the wiring harness.
C. At the machine harness connector for the relay, place a jumper wire between the signal wire and the signal return.
D. Turn the key start switch and the disconnect switch ON. Do not start the engine.
E. Observe the status of the diagnostic code.
The diagnostic code changes from anFMI 5 to an FMI 6 after the jumper wire is installed. OK - The harness is correct. The diagnostic code changes from an FMI 5 to an FMI 6 after the jumper wire is installed. The relay has failed.
Repair - Replace the relay.
Proceed to Test Step 3.
NOT OK - The diagnostic code remains active.
Proceed to Test Step 2.
2. Check The Harness For An Open
A. Turn key start switch and disconnect switch OFF.
B. Disconnect the machine harness connectors from the ECM.
C. The jumper wire remains installed.
D. At the ECM machine harness connector, measure the resistance between the signal contact and the return contact.
The resistance is less than 5 Ω. OK - The resistance is less than 5Ω. The machine harness is correct.
Proceed to Test Step 3.
NOT OK - The resistance is greater than 5 Ω.