MIL Illuminated- ECM Update for P026C, P20EE, or P11D5 – 2021 Chevrolet Silverado & GMC Sierra 2500HD/3500HD

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Service Bulletin Bulletin No.: 21-NA-128 Date: June, 2021 TECHNICAL Subject: MIL Illuminated- ECM Update for P026C, P20EE, or P11D5 Brand: Model: Model Year: VIN: Engine: from to Transmission: from to Chevrolet Silverado 2500HD/ 3500HD 2021 2021 Before 1GC4YTEY5MF261413 Equipped with 6.6L Engine (RPO L5P GMC Sierra 2500HD/ 3500HD 2021 2021 Equipped with 6.6L Engine (RPO L5P Involved Region or Country North America. Israel, Palestine, Middle East, Australia and New Zealand. Additional Options (RPOs) Condition Some customers may comment that the MIL is illuminated. Some technicians may find DTC P026C, P20EE, or P11D5 Cause The cause of the condition may be a software anomaly Correction Please check for any open campaigns and perform as necessary: • If campaign N212336570 or campaign N212331790 applies to this VIN and is open, please close the campaign. Doing this will install the latest ECM update that includes P20EE, P026C, and P11D5 enhancements. • If the campaign is not released for this VIN or if the campaign is already closed, please check for an ECM update. Reprogram the Engine Control Module (ECM). Service Procedure Caution: Before downloading the update files, be sure the computer is connected to the internet through a network cable (hardwired). DO NOT DOWNLOAD or install the files wirelessly. If there is an interruption during programming, programming failure or control module damage may occur. • Ensure the programming tool is equipped with the latest software and is securely connected to the data link connector. If there is an interruption during programming, programming failure or control module damage may occur. • Stable battery voltage is critical during programming. Any fluctuation, spiking, over voltage or loss of voltage will interrupt programming. Install a GM Authorized Programming Support Tool to maintain system voltage. Refer to www.gmdesolutions.com for further information. If not available, connect a fully charged 12 V jumper or booster pack disconnected from the AC voltage supply. DO NOTconnect a battery charger. • Follow the on-screen prompts regarding ignition power mode, but ensure that anything that drains excessive power (exterior lights, HVAC blower motor, etc) is off • Clear DTCs after programming is complete. Clearing powertrain DTCs will set the Inspection/ Maintenance (I/M) system status indicators to NO. Caution: Be sure the VIN selected in the drop down menu (1) is the same as the vehicle connected (2) before beginning programming. Page 2 June, 2021 Bulletin No.: 21-NA-128 5743643 5644477 Bulletin No.: 21-NA-128 June, 2021 Page 3 5431207 Important: Techline Connect and TIS2WEB screens shown above. Important: If the same calibration/software warning is noted on the TLC or SPS Summary screen, select OK and follow screen instructions. After a successful programming event, the WCC is located in the Service Programming System dialogue box of the SPS Summary screen. No further action is required. Refer to the Warranty section of the bulletin. 1. Reprogram the Engine Control Module. Refer to K20 Engine Control Module: Programming and Setup in SI. Page 4 June, 2021 Bulletin No.: 21-NA-128 5644478 5431209 Bulletin No.: 21-NA-128 June, 2021 Page 5 Note: The screenshots above are an example of module programming and may not be indicative of the specific module that is being programmed. Module selection and VIN information have been blacked out. Important: To avoid warranty transaction rejections, you MUST record the warranty claim code provided on the SPS Warranty Claim Code (WCC) screen shown above on the job card. Refer to callout 1 above for the location of the WCC on the SPS screen 2. Record SPS Warranty Claim Code on job card for warranty transaction submission. Warranty Information For vehicles repaired under the Emission coverage, use the following labor operation. Reference the Applicable Warranties section of Investigate Vehicle History (IVH) for coverage information. 2 years/24,000 miles Federally and 3 years/50,000 miles in California. Labor Operation Description Labor Time *2887368 P026C/P20EE ECM Reprogramming Update 0.3 hr *This is a unique Labor Operation for Bulletin use only. Important: **To avoid warranty transaction rejections, carefully read and follow the instructions below: • The Warranty Claim Code must be accurately entered in the “SPS Warranty Claim Code” field of the transaction. • When more than one Warranty Claim Code is generated for a programming event, it is required to document all Warranty Claim Codes in the “Correction” field on the job card. Dealers must also enter one of the codes in the “SPS Warranty Claim Code” field of the transaction, otherwise the transaction will reject. It is best practice to enter the FINAL code provided by SPS/SPS2. Warranty Claim Code Information Retrieval If the SPS Warranty Claim Code was not recorded on the Job Card, the code can be retrieved in the SPS system as follows: 1. Open TLC/TIS on the computer used to program the vehicle. 2. Select and start SPS/SPS2. 3. Select Settings. 4. Select the Warranty Claim Code tab. The VIN, Warranty Claim Code and Date/Time will be listed on a roster of recent programming events. If the code is retrievable, dealers should resubmit the transaction making sure to include the code in the SPS Warranty Claim Code field. Version 1 Modified Released May 28, 2021

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