John Deere 4520 Error Code 73

John Deere 4520 Error Code 73 Problems

I have a 2011 John Deere 4520 cab with error code # 73. The owner’s manual only shows 1-72. Any idea what it could be? It is intermittent and comes on at various times. Everything seems to be working normally, the battery cables are clean and tight. Hope it’s something we can fix before the dealer has to pick it up.

Any suggestions on what to look for? I have checked the starter relay and the wires going to it and they seem fine. I have tried swapping the relays but the error keeps occurring. The ignition switch and key wiring is fine too. I have never had any problem starting it, the error always occurs while driving it. Maybe a loose wire somewhere else online?

They can be ground wires that are bolted to the chassis next to the battery. The paint had to be polished for a better connection.

Check the cab to the engine ground strap.

If not, check the cab’s main ground point under the steering wheel console (the other side of the ground strap connection).

You can check the ground system by using your jumper wire to connect the battery ground to the cab ground point like a jumper and see if your error 73 stops, mine did then I found the strap problem.

It can be a strap. Take it off and clean both ends. The point where they connect to the block was still painted and the fuel line retainer was installed on top of the ground strap. As a result, there was very little contact between the bolt and the strap (just the edge). Everything else was isolated. Bad design in my opinion. I removed the paint, cleaned the strap and reinstalled it and sprayed it with terminal protector grease to prevent corrosion. I also installed a 4GA cable from the cabin to the same point where the battery ground wire attaches to the frame. There are no more land problems.

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