What Is SPN 157? (Cummins SPN 157 FMI 18 Explained) (2024)

With all the modern technological equipment on car and truck engines these days, it can be confusing when different error codes pop up on your screens. Engines are not simple anymore. It may take a master’s degree in automotive technology to figure out what those codes mean.

This code means- Injector Metering Rail 1 Pressure - Data Valid But Below Normal Operating Range - Moderately Severe Level (source). To properly diagnose and understand the code, you will need the Cummins electronic service tool or its equivalent.

To learn more about this code, just continue to read our article. It explores the topic so you have the right information to handle the problem. take a few minutes to see how this important information can help you solve your engine woes.

What is Cummins SPN 157 FMI 18?

What Is SPN 157? (Cummins SPN 157 FMI 18 Explained) (1)

The definition has been given above and the source has all the instructions to follow to help remedy the situation and get your vehicle back on the road and operating normally. To do this yourself you will need the proper code scanner and reader. Plus, you do have to deal with more than just this fault code.

According to those instructions you also have to “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:

- Fuel: 271, 272, 281, 449, 451, 452, 484, 553, 1911, 2311, 2343, 2372, 3727, 4691, 4726, 5585

- Voltage: 1117

- Sensor supply 6: 515, 516”

There are about 11 more pages of instructions to follow when your truck or car will not start. Also according to that manual, you have 12 more possibilities to check before you are done. Unless you get the source quickly and then you can stop your work.

If you are not mechanically inclined, it would be best to talk to a dealer or professional mechanic as they have spent a lot of time learning these codes and what needs to be repaired.

The instructions and the process may be too confusing for most amateur mechanics to handle. But you are the judge of your mechanical abilities and make sure you know your limits as you could damage other components in your work.

Cummins SPN 157 FMI 18?

What Is SPN 157? (Cummins SPN 157 FMI 18 Explained) (2)

We gave you one meaning to this code but like most error codes, there is more than one meaning behind the letters and numbers. Here are three more possibilities related to this code.

- Fuel Rail Pressure High

- Fuel Rail Pressure Too High

- Fuel Rail Pressure Too High: Engine Injector Metering Rail 1 Pressure Data Valid But Below Normal Operating Range - Moderately Severe Level; Pressure Deviation Too Low (source)

Then also like other error codes, you should not delay in getting this one checked out. There is a possibility of other components being damaged if you let it go for too long. If you are on the road, you should have time to wait till you get to your next stop unless you just started on your journey.

No matter the brand of your truck, RV, or car, if you have a Cummins engine, you should go to an authorized Cummins dealer or repair facility. Let the professionals handle this code as it may be beyond your mechanical expertise.

Even if your plungers are made of titanium, there is always a chance of failure, and not just on rare occasions.

Injector Metering Rail 1 Pressure

What Is SPN 157? (Cummins SPN 157 FMI 18 Explained) (3)

According to one mechanic, per one owner’s story, this is the toughest code to fix. According to that owner’s story, it takes several weeks to figure out what is wrong. The reason for this is that Cummins has created a special checklist for this error code.

Then Cummins monitors the mechanics as they go through this checklist. What that means is that the mechanic has to go through each step and take no shortcuts. On top of that, it takes special equipment to diagnose this error code.

Not every authorized Cummins repair shop close to you has this special equipment or the special tools to fix the problem. What caused this problem in this particular case was a drop in fuel pressure. Sometimes the only fix is replacing the fuel tank.

In another case, found that once the tank was removed and opened up, a small piece of plastic was found inside the fuel tank that impeded the flow of the fuel. That triggered the alert and caused a long repair time.

Finding TheProblem

What Is SPN 157? (Cummins SPN 157 FMI 18 Explained) (4)

It has been said that there is a big difference between a Cummins shop and an authorized dealer. The reason this has been stated is that the former has the specialized tools and equipment to diagnose the problem. The latter is helpful but often lacks those tools and knowledge.

One owner said this about his similar problem-- “that took 3 repair visits and a total of 4 weeks and many hundreds of miles driving back and forth to repair places. My problem was resolved only when we went through three different shops, 3 sets of local mechanics, the field supervisor, the regional service supervisor, the lowest of three Cummins engineering levels, and finally the middle Cummins engineering levels.” (source- Gary.Jones post).

Some Final Words

Not all error codes will be easy to fix. They may not be easy to find either as you just found out. Fortunately for the two owners, the companies they bought their RVs from were very helpful.

This is not a DIY fix. You will have to go to Cummins or their chops to get the problem resolved. Even if it is something simple like plastic in the fuel tank, it may take some time to find the problem. Roadside emergency service companies can be very helpful at this time.

What Is SPN 157? (Cummins SPN 157 FMI 18 Explained) (2024)

FAQs

What is the FMI 18 on a Cummins SPN 157? ›

SPN#157, FMI#18 ― Fuel Pressure Lower Than Commanded Pressure.

What is code 157 on ISX Cummins? ›

Spn code 157 fuel rail pressure fault.

What does code 157 mean? ›

What is Denial Code 157. Denial code 157 is used when a service or procedure was provided as a result of an act of war. This means that the healthcare service or procedure was deemed unnecessary or not eligible for reimbursem*nt due to its connection to a war-related event.

What does FMI 18 mean? ›

In summary, SPN 4364 FMI 18 is an engine error code related to the aftertreatment system of a diesel engine. It can indicate a variety of issues, ranging from a faulty NOx sensor to a malfunctioning DEF system. Symptoms include the illumination of the check engine light and potential engine derate mode.

What does SPN and FMI stand for? ›

SPN is short for suspect parameter number. It identifies which electrical circuit, part or component of your truck isn't working properly. FMI stands for failure mode identifier—this part of the fault code tells you what type of problem your truck has.

How do I clear my Cummins ISX fault code? ›

Using a code reader tool, connect to the ECM and find the “fault codes” tab. The displayed codes can generally be clicked on one by one. Another option is to select “erase all faults” and then follow the onscreen instructions. At the end of the procedure, the ignition key should be turned off.

What does ISX stand for on a Cummins engine? ›

The ISX was originally called the “Signature” series due to the revolutionary fuel system known as the “Interact System” The IS in ISX stands for the Interact System and is in use for on-highway applications.

Where is boost pressure sensor on ISX Cummins? ›

It should be located on the high pressure pipe after the turbo on top near the back of the engine on the exhaust side. If you are having trouble finding it, it may be best to take it to a shop and they can point it out on your truck for you.

What is a 157 error? ›

code 157 indicating that there has been a memory access violation.

What is international code spn 157? ›

The ECM has detected that fuel pressure is lower than commanded pressure. Possibly hard to start or low power. Engine could possibly not start. This is a very complicated fault and you need special tools and cummins insite to properly trouble shoot.

Can I drive with a p0157 code? ›

However, especially if the problem is actually an issue with the air-fuel ratio coming out of your catalytic converter, driving for extended periods of time with these diagnostic codes firing can result in serious damage to your engine. It's best not to risk this and instead to talk to an expert as soon as you can.

What is the code 157 on a Cummins ISX? ›

This is for fuel pressure being low. I would make sure the sensor is not biased. If the sensor is fine I would check the fuel pump actuator connector and make sure it is fine.

What does SPN mean in diesel? ›

SPN stands for Suspect Parameter Number. It's a diagnostic trouble code that provides detailed information about specific faults detected by the vehicle's ECU, making it easier to identify and address issues within the vehicle's electronic systems.

What does FMI mean Cummins? ›

FAILURE MODE IDENTIFIERS (FMI) Now that we have defined MID (The component) and PID (types of data), we can talk about Failure Mode Identifiers (FMI). Every diagnostic trouble code (DTC) that you find will have an FMI.

What is Cummins 3521 FMI 18? ›

According to Cummins QuickServe documentation, SPI 3521 FMI means “The DEF quality sensor has detected that the DEF concentration has fallen below a critical threshold.” So either your DEF is bad or the sensor is bad.

What does spn 102 fmi 18 mean? ›

Intake Manifold Pressure Too Low. Table 2. SPN 102/FMI 18 - GHG14. Description. Intake Manifold Pressure Lower than Expected Under a Load.

References

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