FAQ | John Deere troubleshooting

Question: Why does a John Deere machine with a 9.0L or larger engine smoke after a DPF delete, and how do I fix it?

If you have a John Deere machine with an L21 or L33 ECU and a 9.0L or larger engine, you may notice it blows black or white smoke intermittently after a DPF delete. In this case, the fix is usually simple: locate the DPF fuel dosing valve and unplug connector C.

Applies to

  • John Deere machines with L21 or L33 ECUs
  • John Deere engines 9.0L and larger
  • Machines that started smoking after a DPF delete was performed

Common symptom

  • The machine runs, but every once in a while it starts blowing black smoke or white smoke
  • The issue appears after the DPF delete, not before

Solution

  1. Locate the DPF fuel dosing valve on the machine.
  2. Find connector C on that valve assembly.
  3. Unplug connector C.
  4. Start the machine and verify the intermittent smoke issue is gone.
Tip: If you are tracing the wrong connector or are not sure which component you are looking at, use the photos below to match the valve location before unplugging anything.

Reference photos

Wide view showing the location of the John Deere DPF fuel dosing valve
Wide view of the engine area showing where to find the DPF fuel dosing valve.
Close-up showing the John Deere DPF fuel dosing valve and connector area
Closer view of the valve assembly so you can identify the connector location more confidently.
Diagram showing the John Deere DPF fuel dosing valve connector points
Reference diagram highlighting the fuel dosing valve assembly and connector points.

Quick checks if the issue remains

  • Confirm the machine is in the correct group: L21/L33 ECU and 9.0L or larger engine.
  • Recheck that you unplugged the correct connector on the dosing valve assembly.
  • If the machine still has abnormal smoke after that, inspect the setup further before assuming it is the same issue.

Need help?

If you want TM AG Tuning to check the file or confirm whether your machine matches this case, contact us with the machine details and ECU information.