GM Bulletin Addresses P0604/P0607 Gateway Module Codes on Silverado EV, Sierra EV and Other EVs

If your Chevrolet Silverado EV, GMC Sierra EV, Hummer EV, Equinox EV, Blazer EV or certain Cadillac EVs display a warning after a low voltage event, a new General Motors service bulletin may explain what is happening.

GM has issued bulletin PIT6512A covering diagnostic trouble codes P0604 and P0607 in the K56 Serial Data Gateway Module, or SDGM.

The important part is that GM is not initially treating this as a failed module.

According to the bulletin, the codes can be triggered by a software anomaly in the Serial Data Gateway Module following a low voltage condition or dead battery. GM engineering is working on a software update to address the issue.

In the meantime, dealers have been given an interim reset procedure intended to determine whether the module actually needs to be replaced.

What GM Says Is Happening

GM says some customers may see a Service Engine Soon or Malfunction Indicator Lamp illuminated on the Driver Information Center.

When the vehicle is scanned, technicians may find DTC P0604 and/or P0607 stored in the K56 Serial Data Gateway Module.

According to GM, this can occur following a low voltage event.

The bulletin identifies the cause as a:

Software anomaly in the Serial Data Gateway Module.

It is important to note that a stored module fault code does not necessarily mean the SDGM itself has failed.

GM also does not identify a specific propulsion or drivability problem in this bulletin. The condition described is the warning indicator and the corresponding diagnostic codes.

Which GM EVs Are Covered?

PIT6512A applies to a fairly large number of Buick, Cadillac, Chevrolet and GMC vehicles. For EV Outdoors readers, these are the battery electric vehicles listed in the bulletin:

This article is focusing on the EV models most relevant to EV Outdoors readers.  GM lists all VINs within the applicable model year ranges in the bulletin.

What GM Is Telling Dealers to Do

GM's current repair procedure is relatively straightforward and is designed to avoid replacing the Serial Data Gateway Module unnecessarily.

Step 1: Verify the Battery Is Fully Charged

GM says P0604 and P0607 can be set following a low voltage condition or dead battery.

Technicians are instructed to make sure the battery is fully charged before continuing with diagnosis.

Step 2: Clear the Codes and Reset the SDGM

If P0604 and/or P0607 are stored as current or history codes, the dealer is instructed to clear the diagnostic trouble codes and reset the Serial Data Gateway Module.

The bulletin specifies performing the reset by removing the appropriate SDGM fuse for 15 minutes and then reinstalling it.

If P0604 or P0607 does not return after the reset, GM says no further action is needed.

Step 3: Replace the Module Only If the Code Returns

If P0604 or P0607 returns as a current code after the previous steps have been completed, GM says the Serial Data Gateway Module will need to be replaced.

However, dealers cannot simply order and replace the module.

The SDGM is currently under a part restriction, which means the dealer must contact GM's Product Quality Center, or PQC, and receive authorization before replacing it.

GM specifically warns technicians not to continue through the replacement process if the reset has already corrected the problem.

GM Is Working on a Software Update

The reset procedure is only an interim solution.

GM says its engineering team is actively working on a software update to address the underlying concern.

The August 2026 bulletin does not provide a release date for that software update.

That means owners experiencing the problem today may receive the reset procedure first, with a more permanent software correction expected later.

Why the Low Voltage Connection Is Important

Modern EVs still depend heavily on their low voltage electrical systems to initialize computers, controllers and communication networks throughout the vehicle.

In this particular bulletin, GM specifically connects P0604 and P0607 in the SDGM with a low voltage event or dead battery.

That makes the sequence of events useful information for both owners and technicians.

If a service warning appears shortly after a low voltage condition, battery problem or loss of electrical power, it may be worth mentioning that history to the servicing dealer along with bulletin PIT6512A.

It also illustrates why replacing a control module simply because a module related fault code appears can be premature. GM's own procedure calls for charging, clearing and resetting the system before authorizing hardware replacement.

Is PIT6512A a Recall?

No. PIT6512A is a General Motors service bulletin, not a recall announcement.

Service bulletins provide technicians with diagnostic and repair information for conditions that may occur on certain vehicles.

GM specifically cautions in the document that owners should not assume the bulletin applies to their vehicle simply because their model and model year appear on the list.

In other words, having a 2024-2026 Silverado EV or Sierra EV does not mean your truck has this problem.

The bulletin becomes relevant when the specific condition and diagnostic codes described by GM are present.

What Should Owners Do?

If your vehicle is operating normally and you have not experienced the warning or related diagnostic codes, this bulletin by itself is not evidence that your vehicle requires repair.

If you do experience a warning, particularly following a low voltage event, the important information to give your dealer is:

• When the warning appeared
• Whether the vehicle recently experienced a low voltage or dead battery condition
• Any diagnostic codes you were able to retrieve
• GM bulletin number PIT6512A

Owners should also avoid assuming that the Serial Data Gateway Module automatically needs replacement.

GM's current procedure specifically calls for diagnosis and a reset before module replacement is considered.

The bulletin itself is written for professional technicians and GM cautions against treating it as a do it yourself repair procedure.

What About Warranty Coverage?

GM's bulletin includes labor operations for both the SDGM reset and module replacement when the vehicle is repaired under applicable bumper to bumper warranty coverage.

Actual warranty coverage still depends on the individual vehicle and its warranty status. GM instructs dealers to verify applicable coverage through the vehicle's warranty history.

EV Outdoors Takeaway

The biggest takeaway from PIT6512A is that P0604 or P0607 in the Serial Data Gateway Module does not automatically mean a control module has failed.

GM has identified a software anomaly that can cause these codes following a low voltage event, and its current procedure is designed to reset the system before replacing hardware.

For Silverado EV, Sierra EV, Hummer EV and other affected GM EV owners, this is a useful bulletin number to keep in mind if a warning appears following a low voltage or dead battery event.

The other important piece is that this is not yet the final fix.

GM says engineering is working on a software update. We'll continue watching for a revised bulletin or software release that provides the permanent correction.

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Sources and Methodology

Manufacturer Communication Record: NHTSA manufacturer communication ID 11036194. View the official NHTSA bulletin .

This article focuses on the electric vehicles included in PIT6512A. The original bulletin also includes additional Buick, Cadillac, Chevrolet and GMC vehicles.

Technical service bulletins are intended to provide repair and diagnostic guidance to trained technicians. A model being listed in a bulletin does not mean every vehicle of that model has the described condition.