2017 - 2021 GM L5P ECM & TCM Install Instructions

2017 - 2021 GM L5P ECM & TCM Install Instructions


L5P E41 TUNED ECM & TCM Installations


This ECM/TCM has been preprogrammed and is ready for installation. Following installation, no flashing will need to be done with your HP Tuners device. If you have any questions, please create a ticket to speed up the process at this link: https://www.ppei.com/#ticket

Required Tools for Full Installation

·      The Truck

·      T10 Screwdriver/Bit

·      10mm socket (2017-2019)

·      7mm socket (2020+)



2020+ GM L5P’s require the Air Filter Life System to be disabled before you remove your ECM. This does not apply to the 2017 – 2019 GM L5P models. Failure to disable the Air Filter Life System will cause a warning light that can ONLY be reset by a GM Dealer. Please follow these steps if you have a 2020 or newer GM L5P.

1.     With the truck turned on and the engine running, use the dash info screen and navigate over to the settings option ⚙️.

2.     Now with the display showing the setting options – Select “Info Page Options”.

3.     Verify that the “Air Filter Life” is checked – “”.

4.     Navigate over to theinformation tab and scroll down until you find the “Air Filter Life”.

5.     Click on the “Air Filter Life” and select “Disable”.


Step 1 - ECM Removal (if you selected ECM Exchange please skip this step)

1.     With the keys removed from the ignition, pull the hood release latch located near the OBDII port. Open the hood (optional - If hot - allow the truck to cool down for a minimum of 30 minutes before proceeding).

2.     Locate the Factory ECM:

                                                                                                     i.      Figure A for 2020+ Models

                                                                                                   ii.      Figure B for 17-19 Model


FIGURE A: 2020+ Model Trucks (Standing in front of the truck, facing the engine, the ECM will be located behind the driver-side headlight. Using a T10 screwdriver/bit, remove all eleven (11) of the screws holding the driver-side inner fender in place.


·      Remove the three plugs that are connected to the ECM.

·      Removing The ECM - Using a 7mm socket – locate and remove the four (4) bolts securing the ECM in place (bolts are located on each corner)



FIGURE B: 17-19 Model Truck (Standing in front of the truck, facing the engine, the ECM will be located behind the driver side headlight, below the upper coolant radiator hose, between the battery, and the power steering fluid reservoir (PSR). See Below.




·      Remove the three plugs that are connected to the ECM. (For ease of removal and installation, it may be easier to disconnect the TCM connector and pull the harness back towards the firewall to make for more workspace).

Step 2 – Install Tuned HP Tuners ECM

1.     Install the modified HP Tuners L5P E41 ECM the same way as the factory ECM was removed.

2.     ECU Installation is complete- This ECM has been preprogrammed and DOES NOT require any flashing using your HP Tuners device.

Step 3 – ECM Immobilizer learn

1.     Perform an Immobilizer Relearn (GM Dealer Tool or SPS Subscription Required) - If you do not have access to either, please continue following the provided steps below.

2.     If neither GM Dealer Tool nor SPS Subscription are available at this moment during installation, please contact your local GM Dealership and speak to the service department. Request and schedule a time to have the Immobilizer relearned at the local GM dealership. Dealer Locator link: Note – a Chevrolet dealer can provide Immobilizer relearn for a GMC and vice versa.

a.     Chevrolet Dealer Locator – https://www.chevrolet.com/dealer-locator

b.     GMC Dealer Locator – https://www.gmc.com/locate-gmc-dealer

3.     If the Immobilizer relearn hasn’t been completed, the vehicle will start and run as normal, however, the remote start function will not work until the immobilizer relearn is performed.


17-19 Tuned TCM Installation

Step 1 – Locate the TCM

1.     Use the attached pictures below to help locate your TCM. Depending on the year model it will either be located on the back of the fan shroud or attached to the firewall behind the fuse panel.


2.     Disconnect the harness from the TCM and push up on the two tabs holding it into its holder so that it can be removed.

3.     Install the modified HP Tuners L5P TCM the same way as the factory TCM was removed.

4.     TCU Installation is complete- This ECM has been preprogrammed and DOES NOT require any flashing using your HP Tuners device.

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