How To Clear Cummins Fault Codes (How To Read SPN Codes)

No matter who is to blame, the car or truck owner is stuck with clearing those fault codes that let them know what is wrong with their vehicle.

To clear fault codes, you would need a code reader, a scanner, or a software and diagnostic tool. Sometimes they are all the same. Once it is connected to the ECM, you go to the fault code tabs and start clearing codes. This can be done one at a time or you can use the clear all codes function.

To learn more about this topic, just continue to read our article. It has the information you want to know about so you can do this task yourself or you can monitor the mechanic who is doing it. Either way, those codes will be cleared and you can drive again.

What Are SPN Codes?


The letters SPN stand for suspect parameter number and this number identifies the specific engine or transmission component that is causing the problem. It may also identify the specific condition that is doing the same thing.

You will see the number and look it up on the code sheet and that sheet will have the name of the component on it. The confusion may come in when the SPN number indicates a condition and not a part. It is easy to find the part once it is identified but it is not easy to find the location of the condition.

You may have to look at some different numbers which are also a part of the code that is triggered to get the right location for the condition causing you all these problems.

What also complicates finding the right code explanation and identification is that there are over 50,000 SPN numbers and they are all used by different manufacturing companies.

While those companies are all automotive-related, they may not use the same code for the same problem on their vehicles. Then to make things worse, you may not find all the SPN codes in numerical order.

Or those lists may not present all the sub code numbers for that specific SPN number. Then you have to spend a lot of time searching for the identification and explanation of the code.

Let's just say that modern technology and up-to-date emissions and other regulations have done no one any favors.

What Does SPN Mean in Fault Codes?

As you know by reading the previous section, those letters mean suspect parameter number. For the most part, that number is very helpful and you do not always need the FMI code behind it to have a problem or a code triggered.

Sometimes, the SPN code will be the only number you will get and that usually means that the computer is not exactly sure what the condition is or what is wrong with that part.

That could be due to a communications error or some other reason. That is that part of the meaning of this code. When you see an SPN number pop up on your dashboard’s screen, you know that there is a problem with one of the systems in your engine, transmission, DEF system, and so on.

This number may give you the name of the part but it also may need some additional code numbers to clarify clearly what is wrong. You may see PID or SID, MID, or FMI code numbers as well.

Like the SPN code, those letters and the numbers that follow them are giving you as much information as possible as to the failure taking place under the hood. Without these codes, you may never find the problem.

That is how complicated the modern engine has become. Because of the emissions and other regulations, modern technology has had to create new parts and connect them to an onboard computer or two to monitor what is going on.

You certainly won’t be able to monitor everything included in these modern engines. It is best to learn some of the common codes and have a list nearby to help you figure out the rest.

How To Read Cummins Fault Codes


This can get complicated. There are several reasons for saying this. The first thing you need to know is that Cummins has created its own fault code list. It is usually a 4-digit number but it can be 3 and 5 digits as well.

When you go to a Cummins fault code list, their codes may be in proper numerical order. But the SPN codes they equate to will not be in that same numerical order.

What that means is that you need to know the Cummins fault code and not the SPN or FMI code. Then you follow the numbers for Cummins down to the matching code on the data sheet. Move across the columns to read the SPN & FMI code numbers.

Then there will be a column for the color of the warning light as well as the identification of the part and condition. There will also be a description of the problem in the next column after the identification column.

Everything is written in mechanic’s English so it should be understandable and some people may have difficulty as it is in mechanic’s shorthand. But this is the easy part to read their codes.

The difficult part depends on the year your engine was made. There is a different list and meaning depending on those model years. Prior to 2002, the Cummins engines did not have an EGR and the fault code for those engines is different from the 2007 to 2010 models.

Then when each new engine model is introduced, these fault code lists get updated and provided with even more detailed information. To find the right list, you need to know when your engine was made.

How To Clear Cummins Fault Codes

Clearing fault codes may be a lot easier than finding the right list, looking up the Cummins code number, and then trying to understand the descriptions. The first step in clearing these codes is to make the repairs the codes are warning you about.

Then you have to connect a code reader, scanner, or whatever they are calling this diagnostic tool. You connect it to the ECM or Engine computer module and turn it on.

You may have to manipulate the screen till you get to the fault code tab and click on it. Depending on the type of reader you are using, you simply click on the displayed codes and erase them one by one.

Some of these code readers may have a clear all button you can push and save some time. There should be instructions on your screen to follow to clear the codes no matter which option you choose to use.

Part of those instructions includes the following:

- Close the doors and insert the key into the ignition

- Cycle the key five times from “off” to “run” without actually cranking the engine

- On the fifth cycle, leave in run

Be aware that the ‘run’ part of the ignition is two clicks of the key while the Accessory is only one click.

How do You Reset The Fault Code on a Freightliner?


This system may be different depending on the model of Freightliner you own. Since Freightliner has not gone out of business, reset procedures may not be the same for all model years.

The basic reset for the ECM would be to turn the engine off and disconnect the battery cables. Then leave those cables off for 15 minutes before reconnecting them. That should reset and clear all codes in your ECM. If you want to reset your ABS warning light then here is what you do:

1. Jumper cables-

- Make sure you have jumper cables for the DLC or an adapter kit for service.

- Turn off the truck and install the wires

- The ABS or anti-lock braking system is now blinking

2. Press the brake

- Press down the brake pedal, do not be rough, and do not touch the gearbox and the accelerator.

- After it clicks, push down the brake pedal eight times within a few seconds

- The ABS light should not be off

If that doesn’t turn the ABS light off, then you should talk to a professional Freightliner mechanic to get the problem solved. Also, you can talk to them about clearing codes as well.

If Freightliner is like Cummins, you will need a code reader to help you do that.

How To Clear Cummins Fault Codes Without a Scan Tool

The first step in this process is to make sure you are parked on level ground. You do not want the vehicle to roll away while you are working. Then open your hood and remove both battery cables.

Do the negative one first and put it somewhere it cannot touch the positive cable when it is unhooked. The third step will be to cycle your engine 2 to 5 times depending on your make and model of vehicle.

Step four has you pressing the horn to drain any remaining power in your ECU. This will take anywhere from 30 to 60 seconds and hopefully, you can stand the noise.

Step five, replace the battery cables on your battery, starting with the positive and then the negative. Finally, start your car and let it warm up. By the time it does warm up, the codes should disappear from the screen.

If the check engine light is still on, then you probably did not drain the ECU of all its power. That means you have to do this process all over again. OBDI cars all you have to do is remove the battery cables for a while.

But after 1996 vehicles were put on the OBDII system and this is the process for clearing those codes.

6.7 Cummins Check Engine Light Reset


The best information we have so far is that all you have to do is turn the key on and off 3 times without starting it and the light should go out. Make sure to leave the key in the ‘on’ position the third time.

The rest of the instructions go like this and it is hard to translate without ruining the information:

You will see ---------- in the odo window if you did it correctly. Watch that window and you will see a code come up then ----------- again and if there is more codes you will see them then when it is finished you will see ---done---- in the odo window.”

(source- post #7)

Clearing Engine Derate Cummins

You may need what is called the DTC plus AFT reset tool for a Cummins engine to be able to do this task. This tool is the dealer-level capability and you should be able to access the advanced parts of your ECM to clear any derate codes.

This tool can be used anytime and anywhere so you may be spared the horror of being stuck in the middle of nowhere with a dealer no closer than 200 miles away.

You may be able to use other scanners or code readers as well but that will depend on their capability level. If you do not have that reset tool, then you would have to get to your dealer as soon as possible.

Some Final Words

Clearing codes is easy if you have the right instructions and the right reset tools. Many engine makers try to make DIY clearing of codes impossible that is why dealers have the best code readers you can get.

One reason they do that is to protect you from making a diagnostic and repair mistake. If you make a mistake, the repair by professionals will be far more expensive than the original problem. Blame technology for this complicated system.

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