LZ0 Gets Calibration Updates For 2025 SUV's - 3.0 Duramax Diesel

General Motors has released Service Bulletin #26-NA-033 to provide information on Engine Control Module (ECM) calibration updates for 2025 model-year SUVs equipped with the 3.0L LZ0 Duramax diesel. The bulletin applies to select Chevrolet and GMC full-size SUVs sold in North America and addresses multiple diagnostic trouble codes (DTCs) that may be present due to a software-related anomaly.

This bulletin is informational only and does not automatically indicate a mechanical or component-level failure.

Vehicles Affected

Brand / Model / Model Year

• Chevrolet Suburban — 2025

• Chevrolet Tahoe — 2025

• GMC Yukon — 2025

• GMC Yukon XL — 2025

Engine: 3.0L Duramax Diesel (LZ0)Transmission: AllRegion: North America

Condition

Some customers may comment on the Malfunction Indicator Lamp (MIL) being illuminated.

Some technicians may observe one or more of the following diagnostic trouble codes set as current or in history:

• P059F

• P060C

• P1498

• P2264

• P226D

• P228A

• P228B

• P228C

• P228D

These DTCs may appear without consistent driveability concerns and may not be linked to a confirmed hardware failure.

Diagnostic Trouble Codes Explained

The following descriptions are provided for context and search clarity. Per GM, the presence of these codes alone does not confirm component failure when related to the software anomaly described in this bulletin.

DTC P059F

Active Grille Air Shutter PerformanceIndicates the ECM has detected improper operation or feedback from the active grille shutter system, which is used for aerodynamic efficiency and thermal management.

DTC P060C

Control Module Main Processor PerformanceSet when the ECM detects an internal processor performance issue. This code is frequently associated with calibration or software irregularities rather than physical ECM failure.

DTC P1498

Particulate Matter Control Module Internal Supply Voltage CircuitIndicates a voltage concern detected within the particulate matter control system, part of the vehicle’s emissions strategy.

DTC P2264

Water in Fuel Indicator Sensor CircuitTriggered when the ECM detects an electrical fault or implausible signal in the water-in-fuel sensor circuit.

DTC P226D

Diesel Particulate Filter (DPF) Deteriorated SubstrateIndicates the ECM believes the internal DPF substrate may be degraded. When set due to calibration anomalies, this does not automatically confirm physical DPF damage.

DTC P228A

Fuel Pressure Regulator Control – Forced Engine ShutdownSet when the ECM commands a shutdown due to a perceived fuel pressure regulation fault.

DTC P228B

Fuel Pressure Regulator 2 Control – Forced Engine ShutdownSimilar to P228A, but associated with the secondary fuel pressure regulator control strategy.

DTC P228C

Fuel Pressure Regulator Control Performance – Low PressureIndicates fuel pressure is detected below the expected range during commanded operation.

DTC P228D

Fuel Pressure Regulator Control Performance – High PressureIndicates fuel pressure is detected above the expected range during commanded operation.

Cause

According to GM, the cause of the condition may be a software anomaly within the ECM. This bulletin does not identify a specific mechanical or electrical component failure as the root cause.

Correction

GM recommends the following diagnostic approach:

1. Check for any active campaigns requiring an ECM update and perform them if applicable.

2. If no campaigns apply, check for available ECM calibration updates.

3. If no updates are available, follow Service Information (SI) for standard diagnostics related to the stored DTCs.

This bulletin does not authorize component replacement by itself.

What This Means for LZ0 SUV Owners

• An illuminated MIL on a 2025 LZ0-equipped SUV does not automatically mean a failed sensor, DPF, or fuel system component.

• GM acknowledges that software behavior alone may set multiple, seemingly unrelated DTCs.

• ECM calibration verification should be completed before parts are replaced.

• Vehicles under warranty typically have ECM updates covered when applicable.

  
  

Technician Notes

• Document whether DTCs are current or history prior to clearing.

• Confirm ECM calibration levels before performing intrusive diagnostics.

• Comply with all International, Federal, State, Provincial, and Local regulations when performing service actions, as outlined by GM.

  
  

Bulletin Information

• Bulletin Number: 26-NA-033

• Version: 1

• Release Date: January 29, 2026

• Subject: Information on the LZ0 SUV Calibration Releases

  
  

DuramaxNews Insight

This bulletin aligns with a growing trend seen on newer LZ0 platforms where post-launch calibration refinements are required as the engine expands into additional vehicle applications. When multiple emissions, fuel, and ECM-related codes appear together, software should be ruled out before condemning hardware.