About 2005 John Deere 7220 RPM issues. We have had trouble keeping the rpm on our 2005 John Deere 7220 – 4.5L stable. I can set the rpm knob to the desired rpm and after about an hour of tractor operation the rpm will go up and down on their own between 50 and 100 rpm. During this period the throttle cannot be adjusted.
Sometimes the tractor can be turned off and the problem disappears for 1-2 hours, but eventually reappears. This problem has been going on for a year and a warning light has finally started flashing. When the light started to blink, we realized that the tractor’s power had been reduced by 40%. We have checked and replaced the fuel filters and there was no water or trash in the filters.
Has anyone else had this problem with their tractor before or have any ideas on what to check? Any information on this topic would be greatly appreciated.
Something similar happened to my 7220. It didn’t show the code when cold, but once it was running for 5 minutes it would drop the power to around 1400rpm, with flashing lights. I used the dash display to get the code (SPN 28 FMI 04 which is Digital Throttle Voltage Out of Low Range) using the toggle switch, blinker, and hazard lights switch. You can find the details of how to do this in the manuals.
SPN 28 is specifically for the cruise control potentiometer (as shown above) which is a $ 38 part. You should check the integrity of the cables and connections. In my case, this part was the problem.
What had me puzzled was that Deere calls this code Digital Throttle, but it’s actually an analog potentiometer, which made me question which device to look at. I finally found it in the manual. If you have the manuals, you can look for ECU 000028.04 (or whatever code you find, 000028.04 is SPN 28 FMI 04). There is a lot of detailed information there.
I hope this helps someone.