What Is Fault Code SPN 3359 FMI 31? (Allison Transmission)

Once those amber and red lights get illuminated on your dash, you need to get more information. That is what the SPN FMI code system is all about. Unfortunately, some of these codes just do not bring the information you need.

You are not going to like the meaning of this code. The official SPN FMI list simply says - Transmission Service (filter Life Monitor). The FMI portion of the code will only state, a condition exists. Which is information you already know about.

To learn more about this code and similar ones related to SPN 3359, just continue to read our article. It explores these codes to give you the best information possible and save you search time. Getting you back on the road quickly is one of our goals.

Allison Fault Code SPN 3359 FMI 31


What happens when you see this code illuminated on your dash along with the check transmission light is you are going on a treasure hunt. Unfortunately, this hunt doe not bring a nice monetary reward.

Instead, it will lead you to a possible source of the problem. This Allison code is very generic and does not tell you anything you do not already know. The only clue you have is the words in brackets- Transmission Service (filter Life Monitor).

However, in this particular case, it may not be the transmission filter that is the problem. It may be a bad connector which is what happened to one owner. His story is long but one shop said the transmission was missing a wire which is almost unheard of.

The real source for this code popping up on his dash was that there was a broken pin connector that would not connect to the #80 connector in the transmission.

If the first diagnosis does not sound right, it probably isn’t or it may not be accurate. Until you do the search, you do not know where the problem lies when this code appears.

Also, this fix may or may not be under warranty and you would have to check with several companies associated with your RV to find out if it is or not. The cost of this repair at that time was $800.

Allison SPN 3359 FMI 1


There are codes that are very straight forward and tell you exactly what is going on in your engine or transmission or other module systems. This is one of those codes.

Allison SPN 3359 FMI on the official code list only says- Transmission Filter Maintenance Required (p088b). But on one data sheet, it defines the code as- Transmission Filter Maintenance Required – Low-Most Severe (3).

We put the words in bold to make sure you caught that discrepancy. The reason for the discrepancy is that the FMI portion of the code refers to oil and not transmission fluid. This may not be an important distinction but we wanted you aware of this issue.

The numbers in the bracket for the first definition are the correct Allison fault code for this problem. The sheet we will link to later, says this fault code is telling you that you have a ‘very deteriorated filter.’

If that is the case, then we understand why the other data sheet, written for US army vehicles only, says this fault code is most severe. Most likely, when you see this code, you need to change the transmission filter as quickly as possible.

If you do not take care of it right away, you may suffer more severe damage to your engine or transmission.

Allison Transmission SPN 3359 FMI 18


According to one sheet of codes, this SPN FMI code may translate into Allison fault code Po88a. If that is correct, then that is the same information as SPN 3359 FMI 16 which also equals Alllison P088a.

On the official SPN fault code list the latter code states- Transmission Filter Maintenance Alert (p088a). P088a means- deteriorated filter. In other words, the problem is basically the same as P088b but not as severe.

You will need to change the transmission filter to get the code to disappear. This Allison code will appear on page 32 of the set of Allison codes we will link to in the next section.

Just so you know, there were no data sheets, no discussion forums, or other information popping up for either SPN 3359 FMI 18 & FMI 16. The best we can say is that if you have doubts about this code, talk to your local Allison repair shop to get more accurate information and repair steps.

This is not a code that you want to drive 500 or even 100 miles when it is illuminated. You can drive locally to the repair shop but long distance is out of the question.

Some Final Words

While some codes are not very informative, others point you to the exact problem you need to deal with. Unfortunately, you never know which is which until you click on the fault code and see what it says in its explanation.

It is fortunate that the official SPN fault code list does place some of Allison’s fault codes in its explanations making finding the reason for the code easier. That link will also provide Allison’s contact information in case you have a problem that is not covered by that manual.

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