FLANGE 4F8925 - Caterpillar

G3606 (3XF),
G3608 (4WF),
G3612 (1YG),
G3616 (4CG) EnginesEffective February 14, 1996, the G3600 group is releasing a new diagnostic strategy that confirms Caterpillar Communication Link Two is active. Caterpillar Communication Link Two is important because it is required to monitor the "Driven Equipment Ready" input to the Engine Supervisory System (ESS). A failure of Caterpillar Communication Link Two will now result in an engine shutdown with a fault code 819-12. This fault code will be described as "Display Data Link Failure".
The Engine Control Module (ECM), Computerized Monitoring System (CMS), Customer Communication Module (CCM), and Digital Diagnostic Tool (DDT) share information over the Caterpillar Communication Link Two. The information exchange between these modules is essential for proper engine operation and for protection of the driven equipment.
819-12 (Flashing) Display Data Link Failure:
* If the engine is running, it will shutdown. The engine will be prevented from restarting until the diagnostic code is cleared by toggling the "Display Select Switch".* A "RST REQRD" diagnostic will also be present on the ECM to indicate the system must be reset before restarting. Momentarily turn the Mode Control Switch (MCS) to the "Off/Reset" position to reset the system.* On systems equipped with the standard warning horn function, the alarm output will be energized until the diagnostic code is cleared by toggling the "Display Select Switch".Conditions That Generate This Code:
* The ECM has been unable to communicate successfully with the CMS.Probable Causes For This Fault:
* An open/short in the communication link (+) and communication link (-).* Failed ECM, CMS, CCM, or DDT.Functional Test:
1. Remove power from the control system. Turn the MCS to the "Off/Reset" position and open the fuse breaker in the ESS panel.2. Disconnect the DDT, ECM connector J3, CMS, and CMM. Check for corrosion or mechanical failure.3. Using an ohmmeter set on the 10 Ohm scale, measure the resistance between ECM connector J3 pin 21, CMS connector pin 23, ESS terminal 358 (+ serial on CCM), and ESS terminal 172. The ohmmeter should indicate less than 2 Ohms resistane between any two of these points.4. Next measure the resistance between ECM connector J3 pin 20, CMS connector pin 24, ESS terminal 357 (- serial on CCM), and ESS terminal 171. The ohmmeter should indicate less than 2 Ohms resistane between any two of these points.5. With the ECM and CMS connectors disconnected, use an ohmmeter set on the highest scale to measure the resistance between ECM connector J3 pin 21 and J3 pin 20. The ohmmeter reading should be greater than 1 million Ohms.6. Connect the ECM and CMS connectors and apply power by closing the fuse breaker and turning the MCS to the "Stop" position. If a fault code appears, open the fuse breaker, disconnect the CMS module, and connect the DDT. Verify DDT communications is operational. If DDT communication is not operational replace the ECM.7. If the ECM and CMS are communicating, connect the DDT. If