2017-2023 CHEVY / GMC L5P DURAMAX (WILL NOT WORK ON L5D)

Includes 4 week Tuning support pack! 

LIFETIME SUPPORT PACKAGE (available upgrade) 
This recommended upgrade offers unlimited flashes and basic tune revisions on ALL TUNES. You’ll receive automatic tune updates so that you can take advantage of the progress that we make and enjoy the timelessness of the EZ LYNK AutoAgent 3.

TCM TUNING
This HIGHLY recommended upgrade will increase the line pressure in your transmission so it can keep up with all the added power your engine will be producing from the tunes. We highly recommend TCM tuning to anyone that plans on running anything more than a tow tune. Please specify if you have any transmission modifications when ordering TCM Tuning.

POWER LEVELS
Stock
30hp
60hp
90hp
120hp
150hp
SOTF (Change tunes via cruise control buttons) 

ATTENTION!

Note: 17-18 with the ECM PN ending in 12676723 have to be sent into EZlynk for an unlock on their bench. They are not currently flashable on EZlynk.

EZ is releasing firmware updates for these pretty regularly so this product should get any small unlocking/tuning issues worked out in the immediate future.

If you have a flashing issue Ezlynks tech support number is: 877-207-5530

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2017–2023 Chevy/GMC L5P Duramax EZ LYNK Flashing Guide

Before You Start

1. Do not rush the flash

Plan for the truck to sit undisturbed for 30–60 minutes.

Do not start this process if you are in a hurry, if the batteries are weak, or if you do not have a charger/maintainer connected.

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2. Connect a good battery maintainer or programming power supply

This is very important on L5P trucks.

Before flashing, connect a quality battery maintainer or regulated power supply.

Do not use:

• A cheap trickle charger

• A jump box

• A charger in “engine start” mode

• Anything that causes voltage spikes or unstable voltage

The truck needs stable voltage the entire time. Weak batteries or voltage drops are one of the most common reasons these trucks fail to take a flash.

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3. Turn off all electrical loads

Before flashing, turn everything off:

• Headlights off

• Auto headlights off if possible

• HVAC off

• A/C off

• Defrost off

• Heated/cooled seats off

• Radio off

• Interior lights off

• Phone chargers unplugged

• Dash cameras unplugged

• Radar detectors unplugged

• Aftermarket lights/accessories off

• Amplifiers, compressors, GPS units, or other add-ons unplugged or powered off

Close the doors and leave the truck alone during the flash.

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4. Make sure the cooling fans are OFF

Do not flash the truck with the cooling fans running.

If the fans are running:

• Turn HVAC off

• Turn A/C and defrost off

• Let the truck cool down

• Cycle the key off and wait

• Do not continue until the fans are off

Fans running can create a large voltage draw and cause flashing problems.

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Flashing Instructions

Step 1: Install the Auto Agent app

Download the Auto Agent app on your phone.

Log in or create your EZ LYNK account.

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Step 2: Put the truck in RUN, engine OFF

Do not start the truck.

For keyed trucks:

1. Insert the key.

2. Turn the key to RUN / ON.

3. Do not crank the engine.

For push-button trucks:

1. Do not press the brake pedal.

2. Press and hold the start button until the truck goes into RUN / ON mode.

3. Make sure the engine stays off.

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Step 3: Plug in the EZ LYNK AutoAgent

Plug the EZ LYNK AutoAgent directly into the OBD-II port.

Make sure it is fully seated.

You should see the device power up.

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Step 4: Connect your phone to the EZ LYNK Wi-Fi

On your phone:

1. Open Wi-Fi settings.

2. Select the EZ LYNK / AutoAgent Wi-Fi network.

3. Connect to it.

Your phone may say No Internet Connection while connected to the EZ LYNK Wi-Fi. That is normal. The phone is connected to the AutoAgent, not normal internet.

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Step 5: Open the Auto Agent app

Open the Auto Agent app and make sure the truck shows as connected.

If it does not connect:

1. Leave the key in RUN.

2. Unplug the AutoAgent.

3. Plug it back in.

4. Reconnect your phone to the EZ LYNK Wi-Fi.

5. Reopen the Auto Agent app.

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Step 6: Link to the technician if needed

If your device has not already been linked:

1. Open the Auto Agent app.

2. Go to the menu.

3. Go to Vehicle.

4. Go to Technicians.

5. Select Lynk.

6. Enter the technician email: ezlynkconnect@gmail.com

7. Submit the request.

Once linked, the tune files will be made available in the app.

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Step 7: Download the tune file before flashing

Go to:

Menu → Vehicle → ECU Profiles

Select the correct tune file for your truck.

If there is a cloud/download button, download the tune file first.

If the file will not download while connected to the EZ LYNK Wi-Fi:

1. Disconnect from the EZ LYNK Wi-Fi.

2. Connect your phone to normal cellular/Wi-Fi internet.

3. Download the tune profile.

4. Reconnect to the EZ LYNK Wi-Fi before installing.

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ECM Flash

Step 8: Flash the ECM first

Before pressing install, confirm:

• Battery maintainer/power supply is connected

• Fans are off

• HVAC is off

• Lights are off

• Doors are closed

• Aftermarket accessories are unplugged/off

• Phone is charged

• Phone is connected to EZ LYNK Wi-Fi

• Correct tune file is selected

• AutoAgent is fully plugged in

Then:

1. Select the correct ECM tune file.

2. Press Install.

3. Follow the app prompts exactly.

During the flash:

• Do not open the doors

• Do not press the brake

• Do not start the truck

• Do not unplug the AutoAgent

• Do not disconnect the charger

• Do not walk away with the phone

• Do not switch apps if avoidable

• Do not cycle the key unless the app tells you to

Let the flash fully complete before touching anything.

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Step 9: After the ECM flash completes

Once the app says the flash is complete:

1. Follow any key-off/key-on prompts.

2. Turn the key off when instructed.

3. Wait 2–5 minutes.

4. Let the truck modules settle.

5. Start the truck only after the app says the process is complete.

Some warning lights or messages may appear immediately after flashing. That can be normal until the truck is cycled and codes are cleared.

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TCM Flash

Step 10: Flash the TCM if your package includes TCM tuning

If your order includes TCM tuning, flash the TCM after the ECM flash is complete.

Do not assume the ECM and TCM flash together. On many Duramax trucks, the ECM and TCM files are separate.

To flash the TCM:

1. Keep the charger/power supply connected.

2. Put the truck in RUN, engine OFF.

3. Make sure fans are off.

4. Make sure HVAC/lights/accessories are off.

5. Connect your phone to the EZ LYNK Wi-Fi.

6. Open the Auto Agent app.

7. Go to ECU Profiles.

8. Select the correct TCM file.

9. Press Install.

10. Follow the app prompts exactly.

Do not interrupt the flash.

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After Flashing

Step 11: Clear codes

After the truck is fully flashed and starts:

1. Let the truck idle.

2. Use the app to scan for codes.

3. Clear codes.

4. Shut the truck off.

5. Wait a couple minutes.

6. Restart the truck.

7. Recheck for codes.

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If the Flash Fails

If the flash gets stuck at 0%

Do this:

1. Do not start the truck.

2. Leave the charger/power supply connected.

3. Turn the key off.

4. Unplug the AutoAgent.

5. Connect your phone to normal internet/cellular data.

6. Reopen the Auto Agent app.

7. Re-download/fetch the tune profile.

8. Turn the key back to RUN, engine OFF.

9. Plug the AutoAgent back in.

10. Reconnect to the EZ LYNK Wi-Fi.

11. Retry the install.

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If the flash fails partway through

Do this:

1. Do not disconnect the batteries.

2. Do not remove the charger/power supply.

3. Do not keep randomly cycling the key.

4. Take a screenshot of the exact error.

5. Check that voltage is stable.

6. Make sure fans, HVAC, lights, and accessories are off.

7. Reconnect to the AutoAgent.

8. Look for Recovery, Resume, Retry, or Return to Stock options in the app.

9. Try recovery/resume first if available.

10. Contact support before making repeated attempts.

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What to Send Support if There Is an Issue

If the truck has an issue during or after flashing, send us the following:

• Year, make, and model

• VIN

• ECM part number, if known

• TCM part number, if known

• Exact tune file name selected

• Whether you were flashing the ECM or TCM

• Screenshot of the error message

• Battery voltage during the flash, if known

• Whether a charger/power supply was connected

• Whether the fans were running

• Whether any aftermarket accessories were connected

• Whether the truck starts

• Current DTCs after the failed flash

• Screenshot showing the truck connected in the EZ LYNK app

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Final Checklist Before Pressing Install

Before you flash, confirm every item below:

• Truck is on a proper battery maintainer/programming power supply

• Batteries are healthy and fully charged

• Key is in RUN / engine OFF

• Fans are OFF

• HVAC is OFF

• Lights are OFF

• Doors are closed

• Phone is charged

• Phone is connected to EZ LYNK Wi-Fi

• Correct vehicle is selected in the app

• Correct ECM or TCM file is selected

• Tune file is downloaded

• AutoAgent is fully plugged into the OBD-II port

• No aftermarket accessories are pulling power

• Nobody touches the truck during flashing

Please follow these steps exactly. Most L5P flashing issues come from voltage instability, fans running, weak batteries, aftermarket accessories, or the flash being interrupted.