LAMP GP-SIGNAL 1308930 - Caterpillar

Illustration 1 g01647158
Schematic of the Cat Data Link CircuitThis failure results in codes that are logged against an ECM that is not communicating some expected information to the Main Display Module. The Main Display Module cannot communicate with the Engine ECM or the ECM appears to work intermittently. System Response:Certain display features may not function properly.Test Step 1. VERIFY THE HARDWARE AND THE SOFTWARE PART NUMBERS.
Verify that the following information is correct:
The part number of the software for the Main Display Module
The part number of the "engine ECM software"
The part number of the Main Display Module
The part number of the engine ECM Note: Consult the Business Unit that produces the product for the correct part numbers of the configuration software. Expected Result:All part numbers are correct. Results:
OK - All part numbers are correct. Proceed to test step 2.
NOT OK - All part numbers are NOT correct. The part number of the Main Display Module may be incorrect. The part number of the Engine ECM may be incorrect. The incorrect software for the ECM may also be installed. Repair: Replace the incorrect ECM with an ECM that has the correct part number. Flash the correct and most current software. See Troubleshooting, "Electronic Control Module (ECM) - Flash Program".STOPTest Step 2. INSPECT THE HARNESS CONNECTIONS.
Turn the disconnect switch to the OFF position.
Inspect all harness connections that are related to the Cat Data Link. Make sure that the connectors are clean and tight.
Check the connectors for proper mating.
Check the wires at the connector.
Check each wire for nicks or signs of abrasion in the insulation.
Check for moisture at the connector.
Check the connectors for dirty contacts or corroded contacts.
Check each pin and each socket of the machine harness connectors. Expected Result:The machine harness connectors are tight and free of corrosion. Results:
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 the machine harness or replace the machine harness. STOPTest Step 3. CHECK FOR SHORTS TO GROUND.
The disconnect switch remains in the OFF position.
Disconnect the machine harness from all electronic control modules that use the Cat Data Link.
At the machine harness for the Main Display Module, measure the resistance between frame ground and connector contact 8 (wire 944-OR) of the Cat Data Link circuit.
At the machine harness for the Main Display Module, measure the resistance between frame ground and connector contact 9 (wire 945-BR) of the Cat Data Link circuit. Expected Result:The resistances are greater than 5 ohms. Results:
OK - The resistances are greater than 5000 ohms. The harness circuit resistance is correct. Proceed to test step 4.
NOT OK - Any resistance is less than 5000 ohms. The machine harness has failed. Repair: There is a short between frame ground and the Cat Data Link circuit in the machine harness. Repair the machine harness or replace the machine harness. STOPTest Step 4. CHECK FOR A SHORT TO THE +BATTERY CIRCUIT.
The disconnect switch remains in the