Duramax L5P (2017–2023) — HP Tuners Instructions

Duramax L5P (2017–2023) — HP Tuners ECM & TCM Instructions

For 2017–2023 6.6L L5P Duramax Applications

These instructions will walk you through using HP Tuners to:

  1. Connect your MPVI device to your truck.
  2. Read and save your original ECM and TCM files.
  3. Send the stock files to SNO Diesel Performance.
  4. Receive your new calibration files.
  5. Flash the new ECM and TCM files into your truck.

Please read this entire guide before starting.

Part 1 — Before You Start

You will need:

  • Windows laptop
  • HP Tuners MPVI device
  • HP Tuners VCM Suite installed on your laptop
  • Internet connection
  • Battery charger/maintainer
  • Your SNO Diesel Performance DIY Performance Package

⚠️ DO NOT REMOVE ANY FACTORY HARD PARTS BEFORE YOUR TRUCK HAS BEEN FLASHED WITH YOUR NEW TUNE FILES!

Do not attempt to read or flash your truck with weak batteries.

Connect a battery charger/maintainer before beginning. Turn off:

  • Headlights
  • HVAC
  • Radio
  • Heated/cooled seats
  • Phone chargers
  • Other unnecessary electrical accessories

Keep the doors closed whenever possible.

Part 2 — Install HP Tuners VCM Suite

If you have never used HP Tuners before, install the current version of VCM Suite Beta:

https://www.hptuners.com/downloads/

  • VCM Editor — used to read and flash your ECM and TCM.
  • VCM Scanner — primarily used for diagnostics and datalogging.

For the initial stock-file process, you will be working in VCM Editor.

Part 3 — Connect Your MPVI

  1. Connect the MPVI device to your laptop.
  2. Connect the other end to the truck’s OBD-II port under the dash.
  3. Turn the ignition to ON / RUN — DO NOT START THE ENGINE.

Part 4 — Read Your Stock Files

Open VCM Editor, then:

  1. Select Help → Resync Interface. Close the pop-up once complete.
  2. Select Flash → Read Vehicle.
  3. Wait while HP Tuners identifies supported modules (ECM, TCM, etc.).
  4. Select the ECM and TCM required for your package.
  5. Click READ and leave the truck alone until complete.

DO NOT start the engine, turn off the ignition, disconnect the MPVI or laptop, operate windows or accessories, or disconnect the battery charger during the read.

The dash may display warning messages — this is normal.

Part 5 — Save Your Stock File

Once the read is complete, save the file. Recommended naming:

LASTNAME_YEAR_VIN_STOCK_ECM.hpt

Example: SMITH_2021_1GC4YSEY7MF482731_STOCK_ECM.hpt

DO NOT MODIFY THIS FILE. Keep a copy for your own records.

Part 6 — Send Your Stock File

Email your stock file(s) to: snodieselperformance@gmail.com

Include:

  • Customer Name
  • Order Number
  • Year / Make / Model
  • VIN
  • Transmission
  • Tire Size
  • Gear Ratio (if changed)
  • Any additional engine modifications

Attach the actual .hpt file — do not send a screenshot.

⛔ Stop Here

You may drive your truck normally until you receive your tune files. DO NOT remove any hard parts until your ECM has been flashed.

Part 7 — Before Flashing Your New File

  1. Download and save the tune file(s) to your laptop.
  2. Connect your battery charger/maintainer.
  3. Connect MPVI to laptop and truck.
  4. Turn ignition to ON / RUN — ENGINE OFF.
  5. Turn all accessories OFF. Keep doors closed.

Part 8 — Open Your New File

Open VCM Editor → Help → Resync Interface, then File → Open your supplied calibration file.

⚠️ Only flash the file labeled with your VIN. If the VIN does not match, email us before proceeding.

Part 9 — Flash Your ECM

Select Flash → Write Vehicle. Confirm correct ECM is selected. Select Write Entire from the dropdown. Begin the write.

🚫 DO NOT interrupt the flash. Wait for 100% complete. Follow any ignition instructions shown. Then:

  1. Ignition OFF.
  2. Wait 15 seconds.
  3. Restart as instructed.

Part 10 — Flash Your TCM

Repeat the process with the supplied TCM file. Select Flash → Write Vehicle, verify T93 TCM is selected, select Write Entire. Do not interrupt. Once complete:

  1. Ignition OFF.
  2. Wait 15 seconds.
  3. Restart the truck.

Part 11 — First Start

Start the truck and let it idle. Do not rev aggressively. Check for warning messages. If all clear, shut off and begin disassembly.

Something Went Wrong?

If HP Tuners shows Write Failed, Controller Error, Communication Error, Licensing Error, Unsupported Controller, or Upgrade/Unlock Required — STOP. Take a screenshot and contact SNO Diesel Performance with your name, order number, truck year, and the error message.

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