BODY AS 7S5038 - Caterpillar

The FMI -7 diagnostic code is caused by abnormal communications between an ECM and a specific module via the Data Link. The Data Link is not responding properly.Possible Causes for an FMI -7 Diagnostic Trouble Code Are:
Loose harness connections.
Open wires.
Problems with the terminating resistors.
Wires that are shorted to ground.
Wires that are shorted to the battery.
Data link high wire is shorted to the data link low wire.
High resistance across the Data Link.
Interference across the wires for the Data Link.
Incompatible Software.
Incorrect parameter settings.
An ECM has failed (unlikely).
Illustration 1 g03330977
CAN Data Links SchematicTROUBLESHOOTING PROCEDURE
Prior to beginning this procedure, perform a quick visual inspection of the data link circuits. Look for and repair any areas of obvious problems, such as broken wires or disconnected connectors. If no problems can be found, proceed with the following procedure.
Table 2
Troubleshooting Test Steps    Values    Results    
1. Verify The Hardware And The Software Part Numbers (1)
A. The part number of the flash software for the ECMs in question.
B.The part number of all components related to the faulty Data Link Circuit    
All part numbers are correct.     OK - All part numbers are correct.
Proceed to Test Step 2.
NOT OK - A component of the data link circuit has the wrong part number or the incorrect flash software is installed.
Repair: Replace the incorrect component with a component that has the correct part number. Flash the correct software. See the Troubleshooting, "ECM Software - Install" section of this manual for additional information.
STOP    
2. Inspect The Harness Connections
A. Turn key start switch and disconnect switch OFF.
B. Inspect all harness connections related to the Data Link. 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.
H. Check the connectors for dirty contacts or corroded contacts.
I. Check each pin and each socket of the machine harness connectors. Ensure that the contacts are properly installed. The contacts should mate correctly when the two pieces of the connector are placed together.    
The machine harness connectors are tight and free of corrosion and damage.     OK - The machine harness connectors are tight and free of corrosion.
Proceed to Test Step 3.
NOT OK - The machine harness connectors are in need of repair.
Repair: Repair or replace the machine harness.
STOP    
3. Check The CAN Data Link Termination Resistors For An Open Circuit
A. Locate and remove the CAN Data Link termination resistor plugs.
B. Measure the resistance between pin A and pin B on both resistor plugs.    
Each reading is approximately 120 Ω.     OK -
The resistance is approximately 120 Ω. The resistance is correct. Reinstall the termination resistor plugs.
Proceed to Test Step