COUPLING AS 5I7942 - Caterpillar

Conditions Which Generate This Code:This diagnostic code is recorded when the voltage of the sensor supply circuit (T930-WH-18) is below the normal range (nominal 8.3 DCV). Any sensor connected to this supply will not operate. If there is no sensor connected, then this fault can be considered a nuisance fault. The possible causes of this diagnostic code are listed below:
The sensor supply circuit (T930-WH-18) is shorted to ground.
The sensor is faulty.
The ECM is faulty. This is unlikely.Test Step 1. CHECK THE SENSOR SUPPLY OUTPUT.
Disconnect the Product Link Input/Output cable (J2) from the machine sensor cable.
Turn the key start switch to the ON position.
Measure the sensor supply output (J2-1) to verify it is above 7.5 VDC.Expected Result:The sensor supply output measures above 7.5 VDC.Results:
OK - The voltage is above 7.5 DCV when on. The Product Link Sensor Supply and Product Link harness are likely not faulty. The machine harness or the external sensor may be faulty. Proceed to Test Step 3.
NOT OK - The Product Link cable has a possible short to ground. Proceed to Test Step 2.Test Step 2. CHECK THE PRODUCT LINK HARNESS FOR A SHORT TO GROUND.
Turn the key start switch to the OFF position.
Keep the Product Link Input/Output cable disconnected from the machine sensor cable.
At Product Link harness, measure the resistance from sensor supply contact J2-1 (+V) to frame ground and the PL cable J1-2. Expected Result:Each resistance should be greater than 5000 ohms.Results:
OK - The Product Link harness is correct. Proceed to Test Step 3.
NOT OK - There is a short in the Product Link harness J2-1 (T930-WH-18) and a ground source. The possible ground sources are J1-2 (202-BK), and frame ground.Repair: Repair or replace the Product Link harness. Stop.Test Step 3. CHECK THE SENSOR CABLE FOR A SHORT TO GROUND.
Keep the Product Link Input/Output cable disconnected from the machine sensor cable.
At the sensor machine harness, measure the resistance from sensor supply contact J2-1 (+V) to frame ground and the PL cable J1-2.Expected Result:Each resistance should be greater than 5000 ohms.Results:
OK - The sensor and the sensor harness are correct are not shorted to ground. Proceed to Test Step 4.
NOT OK - There is a short in the sensor harness J2-1 (T930-WH-18) and a ground source or the sensor has failed resulting in a short to ground. The possible ground sources are J1-2 (202-BK), and frame ground. Stop.Test Step 4. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE.
Clean the contacts of the harness connectors.
Reconnect all harness connectors.
Turn the key start switch to the ON position.
Operate the machine.
Determine if CID 0269 FMI 04 diagnostic code is present utilizing ET.Expected Result:A CID 0269 FMI 04 diagnostic code is present. Results:
YES - The problem has not been corrected. It is unlikely that the ECM is faulty.Repair: Perform the previous Steps again. If the cause of the diagnostic code is not found, replace the Product Link ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace" Stop.
NO - The diagnostic code is NOT present. The problem does