What is SPN 3696 FMI 13 & How to Solve It?

What is SPN 3696 FMI 13:

SPN 3696 relates to Aftertreatment DEF dosing, and FMI 13 means the signal is unavailable or missing.

This code appears when the ECM stops receiving communication from the DEF controller or dosing module, which can lead to failed regenerations and engine derate.

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Why This Happens

• Failed DEF controller or wiring harness issue.
• Communication dropout on the CAN line.
• Corroded or loose connectors at the dosing module.
• Loss of power or ground to DEF control unit.
• Module failure or reboot due to overheating.

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How to Fix It

1. Check for power and ground at the DEF dosing module.
2. Inspect CAN wiring between the ECM and dosing unit.
3. Test continuity in communication lines and repair any open circuits.
4. Reflash or replace the DEF control unit if unresponsive.
5. Clear the code and verify proper DEF dosing behavior.

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How to Avoid It Before It Happens

1. Keep module connectors sealed and corrosion-free.
2. Perform communication checks during emissions-related service.
3. Replace dosing modules showing intermittent faults.
4. Ensure CAN lines are secured and not rubbing or pinched.