What Is Code SPN 102 FMI 18? (Cummins, Cascadia, DD15)

Fault codes are supposed to be your friend. But you can be overwhelmed by the sheer number of ‘friends’ you have inside your engine. There are a lot of codes to keep up with and sadly, they may not always agree across the brands

The SPN 102 FMI 18 code has to do with your intake manifold. When you see it lit up on your screen it means that Intake Manifold Pressure Lower than Expected Under a Load. You would have to repair any other fault code that may appear before handling this one.

To learn more about this fault code, just continue to read our article. It has the information you want to know about so you know what you need to do when you see it. There are about 20 things to do before this code gets cleared.

What is Code SPN 102 FMI 18?


This code is for your intake manifold and you should only see it when the intake manifold pressure is too low when under load. By under load, you may be hauling or towing something that adds extra weight and works to your vehicle.

The description for this code is the Intake Manifold Pressure is Lower Than Expected While The Engine is Under a Load. What might trigger this code is when your coolant is over 149 degrees F or 65 degrees C.

There are a lot of warnings about personal injury attached to some data sheets. You do have to be careful when working on this problem and make sure you are on level ground as well as in a well-ventilated area.

As we read the data sheet, found at this link, you have a lot of instructions about fixing other problems first before tackling this one. One of those problems comes in at step 8 where you may have to replace the MCM or the Motor Control Module.

While the problem may be simple, there may be other parts that are in need of replacing before you can handle the simple issue. Sorry, we made a mistake. There are 41 steps to solving this simple problem.

There is a lot involved when you see this fault code. There are numerous times when you have to turn the ignition on but leave the engine off.

SPN 102 FMI 18 Cummins


One of the things you will find when you are involved with engine fault codes, some manufacturers use their own systems. Cummins is one of them as this fault code SPN 120 FMI 18 equals Cummins code 125.

This information is taken from their tier 4 fault code list. It says- “Engine Intake Manifold #1 Pressure” “Intake Manifold 1 Pressure - Data Valid But Below Normal Operating Range - Moderately Severe Level”

This problem only seems to affect the QSX 15 & the QSG 12. When it is in effect, you should also see an amber light lit up. You will find that the SPN 102 code has 4 FMI codes related to the Cummins engine.

They all produce the amber light and they all have to deal with the intake manifold pressure. The difference between them is the engines they affect. FMI 3 & 4 affect all 6 engines listed in that source chart and FMI 16 affects only 3 and not one of those three duplicates the FMI 18.

What that tells you is that you may not see some of these FMI codes. But when they do appear, they are for the intake manifold pressure.

SPN 102 FMI 18 DD15


Whether it is this model or another engine model, you are looking at a problem with the intake manifold pressure. In this case, when you see the amber light, it may be telling you that the pressure is too low and that the engine combustion is incomplete.

The possible sources for this problem will be as follows:

- Air intake leaks

- Damaged sensor

- Restriction in the air filter or exhaust

- Fuel filter issues

- EGR plugged ports

- Failed turbo

The data sheet we quoted from earlier is the Detroit Diesel data sheet. It will provide you with their solutions to this code. It seems that if the computer does not indicate the solution, then modern mechanics do not know what to do or what is wrong.

These dealers and mechanics need to call Detroit to get all the information they need to apply the right repair. At least that is what some owners are saying about the quality of repair going into these modern engines.

While the codes are supposed to be your friend, sometimes they just do not provide all the information needed to make the repair. As we said, that data sheet contains over 40 steps to follow to clear the code and make sure the intake manifold is operating correctly.

The Repair Work Needed


If the code refers to an air leak or possibly the turbo not building enough pressure, the fix seems to be quite simple and the cost is reasonable. You just need to seal the leaks or remove the air boot to check the turbine wheel. If it is binding or broken you would need to repair or replace it.

If the problem is with the intake manifold pressure sensor, then you would have to replace it. The new part costs about $50 and only takes a 10 and 12-mm wrench to fix.

Some Final Words

Fault codes are at best a guide to the problem. Sometimes, they do not always provide all the information you need to know. That is when you have to go to the engine manufacturer to get all the data needed to make the right repair.

Not all mechanics will go above and beyond the computer to get your engine repaired. Especially if you are a woman truck driver. You have to watch more than the fault codes these days to get the repair done right.

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