Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSGMC2021SIERRA 3500 HD DENALI, 6.6L ENG VIN YREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS AND FUEL - 6.6L (L5P) DIESEL - REPAIR INSTRUCTIONSREPAIR INSTRUCTIONSENGINE CONTROL MODULE REPLACEMENT

2021 GMC Sierra 3500 HD Denali, 6.6L Eng VIN Y

Engine Control Module Replacement

2021 GMC Sierra 3500 HD Denali, 6.6L Eng VIN YSECTION Engine Control Module Replacement

Courtesy of GENERAL MOTORS COMPANY

Callout

Component Name

Preliminary Procedures

Before removing the engine control module (ECM), perform SPS function Prepare Control Module for Removal, if available.
NOTE:
The Prepare Control Module for Removal function can only be performed when communication with the old control module is still possible.
Before removing engine control module (ECM), record oil life percentage remaining and Fuel Injector flow identifier codes.
Disconnect the negative battery cable. Battery Negative Cable Disconnection and Connection (Duel Battery)Battery Negative Cable Disconnection and Connection (Single Battery)
Front Wheelhouse Liner Replacement

Engine Control Module Bracket Bolt [4x]

CAUTION:

Refer to Fastener Caution .

Tighten
2.5N.m (22 lb in)

Engine Control Module

WARNING:

Refer to Safety Glasses Warning .

RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.