Serial number to310sg948467 One of the Deere backhoes in my stable has lights and alarms. Service codes are: F421 (throttle input below calibration) F9C4 (don't remember the exact wording but some sort of can-bus or communication error) F990 (oil pressure switch shorts to ground) F974 (alternator voltage high) Battery and alternator voltage are perfect running and not. 12.6 volts off, 14 running. The ecu is seeing 16 and 18 volts respectively. My thought is to go after the voltage problem first and then the f9c4 ( dealt with more than a few of this code and they never have had the same voltage problem.) Any ideas where these extra ghost volts are coming from?
Are you sure the alternator is not putting out that voltage and you have a voltage drop somewhere causing the battery to read the correct voltage? Always start with the grounds.
These two may be related. F9C4 codes can be voltage generated. Also make sure the M12 yellow "CAN" wire is not shorted to the R02 Black shielding wire (or any other wire for that matter). Did you compare voltages at the Alternator output and the battery when the code was active? Also compare to the unswitched voltage at the monitor (connector J2 pin A, B03 red wire) as well as the battery voltage reading in the monitor window. Make sure power and grounds to the monitor and the ECU are all good. Make sure that there is not excessive "AC" voltage at the Alternator output (0.5V AC max with ENG at 1500 rpm with all loads "ON"). That can reek havoc with the system as well. Engine ECU on that unit has the latest software so some of the past bugs related to some of the codes should have been addressed with that.
Those readings are directly from the alternator. Engine ecm is also only about 2 or three months old.
But I will check the other ac voltage and monitor pins next time I am next to the machine. Probably be a few days but thanks for the replies.
Actually did not have to check anything. They left the key in the accessory position last night and drained the battery. When I had to go get it restarted for them this morning I only have the f990 code left. (shorted to ground oil pressure switch) Switch should be here tomorrow. Monitor is now showing same voltages as battery and alternator. Thank you, guys.