GM Updates Battery Software to Improve Moisture Detection on Silverado EV, Sierra EV and Hummer EV

General Motors has expanded a high voltage battery software update covering certain Chevrolet Silverado EV, GMC Sierra EV, Hummer EV and Cadillac Escalade IQ vehicles.

GM Service Update N252516700 updates the Battery Energy Control Module, or BECM, with software designed to improve the vehicle's ability to detect moisture inside the high voltage battery enclosure.

The August 2026 revision adds 2026 model year vehicles to the program, expanding coverage to certain 2024 through 2026 Silverado EV, Sierra EV and Hummer EV models.

The update may be completed either through an over the air software update or by a GM dealer using the Service Programming System.

No replacement parts are required for the software update itself.

What Is GM Updating?

The update applies to the Battery Energy Control Module, which monitors the high voltage battery system.

GM describes the condition this way:

An update is available for the battery monitoring software that improves the BECM's ability to detect moisture inside the battery enclosure.

In other words, this is not a battery replacement campaign.

GM is updating the software responsible for monitoring the battery system so that it can better identify a condition involving moisture inside the enclosure.

The repair procedure itself consists of reprogramming the Battery Energy Control Module with updated software.

Which EVs Are Included?

GM lists the following vehicles in Service Update N252516700:

As with other GM field actions, the model and model year alone do not determine whether an individual vehicle is included.

GM instructs dealers to check the vehicle's VIN in Investigate Vehicle History, or IVH, and confirm that the field action is listed as OPEN.

The Update Changes When Certain Battery Codes Are Triggered

There is another important part of this software update.

GM says the new software changes the threshold used to set diagnostic trouble codes P0AA6 and U359E.

Because of that change, a small number of vehicles may set one of these codes after the software update and after the vehicle completes its first sleep cycle.

GM specifically says that this can happen when a vehicle already has a pre-existing condition.

That distinction matters.

The software update is not described as creating the underlying condition. Instead, the revised monitoring software may detect a condition that was already present.

What Happens If P0AA6 or U359E Appears?

GM instructs technicians to check for P0AA6 and U359E before performing the software update.

If either code is already present, the technician is instructed to follow GM's normal diagnostic and repair procedures before completing the field action.

GM also warns that an affected vehicle with a pre-existing condition may set one of these codes soon after an over the air update or dealer programming event.

If that happens, GM says the vehicle will need additional diagnosis and repair.

The bulletin references GM Technical Service Bulletin 23-NA-151 and the applicable Service Information for that diagnosis.

Importantly, any diagnosis or repair required for P0AA6 or U359E is not covered by this specific Service Update. GM says those repairs should instead be handled under the vehicle's normally applicable warranty coverage.

The Update Can Be Installed Over the Air

Owners may not necessarily need a dealership visit just to receive the software update.

GM says involved vehicles can be corrected either through dealer programming or through an over the air, or OTA, software update.

When an OTA update is successfully completed, GM says the field action will be closed in the vehicle's Investigate Vehicle History record.

That is why dealers are instructed to check IVH before performing the procedure. A vehicle that has already successfully received the OTA software may no longer show the service update as open.

If dealer programming is required, GM lists a labor time of approximately 0.3 hour for Battery Energy Control Module reprogramming.

Do Owners Need to Make a Special Dealer Visit?

Not necessarily.

This is an important difference between this Service Update and some of GM's other field actions.

GM says the Service Update includes vehicles in dealer inventory and customer vehicles that return to the dealership for any reason.

The bulletin also explains that Service Update Bulletins are generally intended to be completed when a customer is already at the dealership for a regularly scheduled visit rather than requiring the customer to make a special trip.

Of course, vehicles that receive the software successfully over the air may not require dealer programming at all.

Affected Dealer Inventory Must Be Updated Before Delivery

The rules are different for affected vehicles currently in dealer inventory.

GM instructs dealers to make sure the Service Update has been completed before selling or releasing an affected vehicle.

Vehicles subject to the field action that are in dealer possession must be held and corrected before they can be:

• Delivered to a customer
• Dealer traded
• Released to auction
• Used as a demonstrator
• Released for another purpose

GM Certified Pre-Owned vehicles subject to the field action may also be temporarily de-certified until the required correction has been completed.

Is This a Recall?

No. GM identifies N252516700 as a Service Update.

The bulletin does not describe this action as a safety recall.

It is a VIN specific field action intended to install updated battery monitoring software on certain vehicles.

Because not every Silverado EV, Sierra EV, Hummer EV or Escalade IQ within the listed model years is necessarily included, owners should have their individual VIN checked rather than assuming the update applies based solely on model year.

The Service Update is scheduled to expire on October 31, 2027.

What Should Owners Do?

If you own a 2024 through 2026 Silverado EV, Sierra EV or Hummer EV, or a 2025 through 2026 Escalade IQ, the first step is to determine whether your specific VIN is included in Service Update N252516700.

Your vehicle may receive the software automatically through an OTA update.

If the update remains open when your vehicle is at the dealership for service, an authorized EV dealer can perform the Battery Energy Control Module reprogramming.

If P0AA6 or U359E appears before or after the update, that is a different situation. GM instructs dealers to diagnose the underlying condition using the applicable service procedures.

Owners should not assume that the appearance of one of those codes means the software update damaged the vehicle. GM specifically notes that the revised software may identify a pre-existing condition that was not previously setting the diagnostic code.

EV Outdoors Takeaway

The most important part of N252516700 is what the software is designed to do.

GM is updating the Battery Energy Control Module to improve its ability to detect moisture inside the high voltage battery enclosure.

The update also changes the threshold for diagnostic codes P0AA6 and U359E, which means a vehicle with a pre-existing condition may suddenly report one of those codes after the new software is installed.

That does not necessarily mean the software created a new battery problem. According to GM, the updated monitoring may expose a condition that was already present.

For Silverado EV, Sierra EV, Hummer EV and Escalade IQ owners, this is another reason to pay attention to software updates and to have an EV certified dealer investigate any battery related diagnostic warning that appears after an update rather than simply clearing the code.

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Sources and Methodology

Primary Source: General Motors Service Update N252516700-01, "High Voltage Battery Software Update," August 26, 2026. NHTSA Document ID: 11036348.

View GM Service Update N252516700-01 on NHTSA

The August 26, 2026 revision expanded the field action to include applicable 2026 model year vehicles.

This article summarizes the GM field action and focuses on information relevant to EV owners. Eligibility is VIN specific and should be confirmed through GM's Investigate Vehicle History system by an authorized dealer.

GM states that diagnosis or repair associated with DTC P0AA6 or U359E is not included within this Service Update and should be handled under the vehicle's normally applicable warranty coverage.