Helpful Guide: SPN 641 FMI 7 Cummins (FMI 9, FMI 11, FMI 13)

Many fault codes refer to the electrical systems a vehicle has. One may get the idea that all fault codes deal with electronic sensors or other parts. But not always. This is a mechanical fault that may or may not be easy to fix.

This code is number 2387 of the Cummins fault code. You will find it on page 11 of our comprehensive Cummins fault code list. The Cummins description is “VGT Actuator Driver Circuit (Motor) - Mechanical system not responding or out of adjustment”

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 find the source of the problem quickly. Then make the needed repair just as quickly.

SPN 641 FMI 7 Cummins


The corresponding Cummins code is 2387 and this code should only trigger an amber light. It is a serious problem but not so serious that it will trigger a derate. Most likely the AGT actuator will still work and make many attempts to meet the commanded position.

This part will continue to do that even if the amber light is illuminated. The worst part of this problem would be that the active and stationary regeneration of the after-treatment will not work and be disabled.

This fault code is triggered when the AGT actuator does not meet the commanded position for more than 10 seconds. The only repair steps you can do at this point are to Verify ECM calibration and check the turbocharger actuator and connections.

Then if anything is wrong or out of calibration, remedy those problems so the light will be turned off and the code cleared.

SPN 641 Engine Variable Geometry Turbocharger Actuator 1

This is a combination part and some owners question the validity of changing out the working turbo when it may just be the actuator that is bad. But that seems to be the recommended fix since the actuator may be damaged by the condition of the current turbo.

Here is a diagram of the actuator and its relation to the turbo.

SPN 641 FMI 7 Cummins (FMI 9, FMI 11, FMI 13)

Some people say it is the carbon build-up that blocks the vanes from moving in the turbo and this lack of movement is what damages the actuator. They also say that simply changing the actuator will not solve the problem. The carbon build-up will still be there and the vanes will still not move as they should.

Some mechanics may want to change both parts just to make sure they are covered. They have had little success in just changing the actuator. If the code remains after the parts have been replaced, then that tells you that the turbo actuator was not installed correctly.

Cummins SPN 641 FMI 9


One of the problems with the Cummins comprehensive list is that they do not assign fault codes for the same SPN numbers in numerical order. This fault code is number 1894 and it triggers the amber light.

What it says is- “Engine Variable Geometry Turbocharger

Actuator #1’ and ‘VGT Actuator Driver Circuit - Abnormal update rate’. The reason you are seeing this code is that the turbocharger’s actuator is faulty.

Unfortunately, the best fix is to replace this part. However, this code can also be triggered if the battery is weak, or the connections are corroded or loose. Just clean those connections and tighten them up.

You may have to either recharge the battery or replace it. Keep in mind that this fault code should not have the mechanic replacing the turbo. It is strictly a communications problem.

This lack of communication can have several connection or power issues causing it.

SPN 641 FMI 11


There are two different diagnoses that can be applied to this fault code. One is the Smart Remote Actuator 5 has Restricted and the other is Actuator #1 Root Cause Not Known.

For the former diagnosis, you may have a problem with the software and you should check to see if you have MCM 63.0.1 levels or newer. If it is above that level, then you need to check for other codes first.

Resolve those other codes before moving on. If it is only an SPN 641 FMI 11 code that is present then you are to do the Turbo Hystere test. If the turbo fails the test, then you are to do the following checks and repairs:

Disconnect the turbo actuator harness connector and inspect the harness connector for signs of corrosion, spread, loose or damaged pins, or signs of wire damage.”

SPN 641 FMI 13


The corresponding Cummins code for this fault code is 2449 and all it says is- “Engine Variable Geometry Turbocharger Actuator #1” and “VGT Actuator Controller - Out of Calibration”

The different action for this code is that the red warning light will be triggered. The action you need to take to start solving this problem are:

- Check for primary fault codes

- Incorrect variable geometry turbocharger actuator installation

- Variable geometry turbocharger actuator calibration incorrect

- ECM calibration revision history check

You will need a Cummins code reader to help diagnose the code and to clear all other codes first before addressing this one. The repair for this code may be to replace the variable geometry turbocharger actuator or replace the variable geometry turbocharger.

Or if it is out of calibration, you will need to download the calibration code and update the software.

Some Final Words

This SPN code 641, has about 7 FMI follow-up codes. Usually, these codes refer to the actuator. But if the actuator is bad, you may have to replace the turbo as that may be the source of the problem.

If it is just a faulty actuator, then you just need to replace that part. If you have a Cummins engine in your vehicle, make sure to get the actual Cummins code. That will make it easier to look up and see what is wrong.

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