I have a cat 323f excavator the serial number is CAT0323FKYEJ00391and the check engine light is on. When I checked the codes with the monitor there was a 5856-9 code. Any suggestions what I should check would be appreciated. I haven’t seen this code yet. Thanks
The monitor can also provide a description, which, in this case, is SAE J1939 Data link #3, abnormal update rate. Your gonna need Cat ET hooked up and it'll have to handshake every module. Just a wild guess, but, I suspect the DEF doser module. But, the only way to confirm is by having Cat ET interface with it.
Attached is the diagnostic procedure, ET will likely be required to access the system communication status for devices on the datalink. This machine was built before 2017 so it does not have a DEF quality sensor in the tank if it’s still as shipped. Will need to see other devices on datalink to identify problem.