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Hey Engine Man: I’m Getting an ECU Code on My Combine Engine the Techs Can’t Figure Out!

Successful Farming Engine Man Ray Bohacz has engine grease and field dirt under his fingernails from a life spent repairing vehicles and running a farm. When he’s not busy in the shop, he’s working on maintenance articles and videos for Successful Farming magazine and answering questions from readers. Here’s a recent letter he received.

Letter from Lee Sudman:

I was reading your article in Successful Farming magazine and thought maybe you could help me with a problem with my John Deere combine. I have a 2010 John Deere 9570 combine. I have been experiencing a code of ECU 103.08 that continually pops up on the display monitor. This code means “Engine Fuel Control System Turbo Charge Speed Not Within Specifications.”

This code does not come on immediately after engine start-up but comes on after the combine has run a few minutes. I have had John Deere techs out numerous times, and they are unable to detect any problems. The turbo censor has been replaced.

Response from the Engine Man:

At this juncture I do not think the turbocharger in the combine engine is overspeeding but, instead, the signal coming from the sensor to the ECU is not clean. It either is picking up interference on the wire back to the ECU or the trigger point has an issue.

Please confirm if it is a two- or a three-wire sensor, if possible.

If it is a two-wire sensor, it is a sine wave. If it is a three-wire sensor, it is a Hall effect. I will assume it is a two-wire sensor because most are.

If it is a sine wave, the signal needs to be a minimum of 0.9 volts on each side of the zero crossing (just like a pick-up coil in a gas engine ignition).

If it is a Hall effect, the signal needs to be a minimum of 80% square (it will be a square wave). Did the JD tech use a scope to read the signal?

Do you have a maintenance question? Email Ray Bohacz at

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