What Is Fault Code SPN 5397 FMI 31? (Cummins, Freightliner)

The numbers for the FMI fault code system stop around 20 or 21. But there are numbers that are listed above those two. Those extra numbers are usually labeled as reserved for SAE use. Someone can always throw you a curveball though.

The SPN 5397 FMI 31 fault code is defined as Aftertreatment 1 Diesel Particulate Filter Regeneration too Frequent- Aftertreatment Diesel Particulate Filter Regeneration too Frequent - Condition Exists.

To learn more about this fault code just continue to read our article. It has the information you want to know about so you can get the problem fixed and back on the highway as soon as possible. Take a few minutes to see how this top information will help you solve this problem and have you driving again.

Cummins SPN 5397 FMI 31


The equivalent Cummins code number is 3375 and it is the last code on page 16 of the complete Cummins fault code list we published earlier. The definition the company provides is as follows:

Aftertreatment 1 Diesel Particulate Filter Regeneration too Frequent

Aftertreatment Diesel Particulate Filter Regeneration too Frequent - Condition Exist”

The last two words of that definition are the definition for the FMI 31 code. On the best FMI list, we know of, they list #31 as Condition Exists and it is listed after numbers 22- 30 which are reserved for the SAE to assign new problems.

When you see the code light up, you should see an amber light. According to the ISX15 CM2350 X101 data sheet, the most important step you can take is #1. It reads:

Fault Code 3375 requires that ALL solutions be performed” and this is to be done “regardless if a given solution is within specification or out of specification.”

In this case, the FMI portion of the code is not helpful. Al it says is that a condition exists which is not much help. What that means is that you have to try all 12 steps and verify each step until you resolve the problem.

Actually, there are only 11 steps as the first one is information only. You can find all the steps at this link.

Step #2 has you doing the following:

Turn the key switch ON.

- Connect the recommended Cummins® electronic service tool or equivalent.


- Use the recommended Cummins® electronic service tool or equivalent to read the fault codes.

Then you are to do the next requirements in that step:

Before troubleshooting this fault code, troubleshoot any fault code that is active or has more than one inactive count within the last 25 engine operating hours from the following list:

- Aftertreatment DPF: 5383

- Aftertreatment differential pressure: 1879, 1881, 1883, 3133, 3134, 3135.

- Fuel: 559, 1139, 1141, 1142, 1143, 1144, 1145.

- Intake manifold: 125, 2973.

- EGR: 1228, 1866, 1896, 1898, 2272, 2273, 2274, 2349, 2353, 2357, 2961, 2962, 3136, 3137, 3138, 3342, 3382, 3383

- After treatment DOC: 1925, 1926, 1932, 1963, 1964, 3167

- Turbocharger: 2198, 2387, 2449, 2634, 2635, 2636, 3616

- Exhaust gas pressure: 2373,2374,2554

We are not going to quote all the steps you need to go through for this brand of engine. This is just to give you an idea of what you are up against when the fault code is set.

All the repair information is there in each step so you should not have any trouble working on this fault code.

SPN 5397 FMI 31 Freightliner


This code for this manufacturer stands for- Aftertreatment DPF Regeneration Too Frequent. All this means is that the regen is happening too often and you will need to diagnose the reason why and fix the problem.

The first step in this process will be to “Electronic Service Tool (EST) with ServiceMaxx software. check if the last four characters in the calibration MDR3?” If yours does not have those last four digits then you will need to update the calibration so that those four digits are the last four in your system.

The next step is to use the same electronic fault reader and look for other fault codes. If there are none, then go to step 5, and if there are other fault codes go to the next step.

In step three you will find these special instructions- “ is SPN 132 FMI 11,

13 and 14 present? If so then do the following “refer to the diagnostic manual and

IK1200526. After repairs are complete, retest for SPN 5397 FMI 31”

If they are not present move on to step #4. This step will also have you looking for a specific fault code other than the one in the heading. If they are present, you need to fix those codes first.

In each step, you will be asked to retest for SPN 5397 FMI 31. The good news is that for this brand of truck, you only have 8 steps to go through before the problem should be resolved.

Another piece of good news is that you do not have to do all the steps before releasing the vehicle. It seems that you can stop at any step once the fault code disappears.

The source for all of this information is found at this link. It will provide extra information so you can make sure the repair is done right. The list of parts you may need to repair or replace is at the end of the document.

There shouldn’t be any confusion using this data sheet to help you make your repairs.

Some Final Words

Once you understand the fault code system for your specific brand of vehicle, repairs should go smoothly. It is just a matter of finding the right explanation for the fault code and the best repair steps you can take.

Just be prepared for any surprises like FMI 31. Condition exists is not very helpful and may get you frustrated when you read those words. Just don’t let it frustrate you too much.

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