The Vortec 454

Vortec 7400 / Vortec 7.4 / L29 / L21

Site Updated

Nov 7, 2010

Text Box: Transmission
& Drivetrain
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Computer Control and Tuning (Page 2)

Below are 2 factory Engine Control Modules (ECM) or “Black Box’s” used for the L29 engines between 1996-2000.  Notice there are 4 large connectors and in the 96-97 1 small connector.

|                              96-97 ECM                                |     |                         98-00 ECM                        |

In 98 GM Started using the new style PCM in the F-Bodies (Firebirds / Camaros) and eventually in 99 the trucks with the new line of Vortec Engines (4.8, 5.3, 6.0, 8.1) used them too. These PCM’s are commonly referred to as the 411, 0411 or LS1 PCM. Don’t let that fool you, they were found in a ton of GM vehicles between 98-04. But the best part is GM also used the new PCM in the old Vortec 4.3 and 5.7 that were being used in the Chevy Express and GMC Savanah. This is what gives us a fairly easy way to swap the Vortec 7.4 over to this new PCM by simply changing out the connector on the end of the wiring harness and installing a custom tune in the PCM. (more detail about this later)  The full part number of the PCM is 12200411.  The best way to go about getting your PCM is to find one from an 01-02 Express or Savanah with a 5.7L engine or buy the PCM from someone that can load the Van tune in as a base tune

Below are pictures of the new PCM. Notice there are only 2 large connectors now.

So here’s how you do for this swap (scroll down for more detail on each step):

1. Get a 0411 PCM with the Van base tune.

2. Use one of the following 3 excel files to transfer your ECM connector pins into PCM connectors.

                          96 ECM to 0411 PCM Conversion Spread Sheet (Click to download Excel file) (Click to download PDF file)

                          97 ECM to 0411 PCM Conversion Spread Sheet (Click to download Excel file) (Click to download PDF file)

                          98-00 ECM to 0411 PCM Conversion Spread Sheet (Click to download Excel file) (Click to download PDF file)

3. Connect the new PCM to the new connector, install in the truck and your done.

 

STEP 1

This can be the easiest and the hardest part all at the same time depending what you want, and what you can do yourself.  Here are a few options and the things to consider about each one.

1. Buy a brand new PCM from GM, they will flash it to the correct tune based on the VIN number that you give them (See VIN Note Below).  If you give them the VIN 1GTGG29R221115929 you will get the correct PCM for the swap. The last 6 digits are the sequential or specific to a vehicle part of the number so if you wanted you could make that part match to your trucks VIN)

         - This will require you or a tuner to modify the Van tune from a 5.7L tune to a 7.4L tune.

         - Brand new PCM’s are expensive especially from the dealer.

 

2. Buy a junkyard PCM from an 01-02 Express or Savanah.

         - This will require you or a tuner to modify the Van tune from a 5.7L tune to a 7.4L tune.

         - Junkyard PCM’s can be hit or miss depending on if they used a screw driver or a sledge hammer to remove it.

 

3. Buy a junkyard PCM from anything with a 0411 PCM and send to someone or a dealer to have the Van tune loaded in.

         - This will require you or a tuner to modify the Van tune from a 5.7L tune to a 7.4L tune.

         - Junkyard PCM’s can be hit or miss depending on if they used a screw driver or a sledge hammer to remove it.

         - This will make it very easy to find a PCM at the lowest cost as long as you know what your looking for.

 

4. Buy a PCM from someone that sells them with the Van / 7.4 base tune installed.

         - If you just want a stock type tune and have no intentions of moding or tuning in the future this is probably your best bet.

 

VIN Note: Most of the tuning software out there allows you to change the VIN number that is stored in the PCM. If you or your Tuner are using HP Tuners to edit the PCM you will not be able to make the VIN in the PCM match the VIN of your truck because of the way that HPT looks up the VIN.

 

 

STEP 2

Determine if your truck is a 96, 97 or 98-00 (that should be easy) and then download the appropriate file. I suggest printing it out. I made the PDF’s so that the sheets are divided by connector with some room for notes on each sheet.

Now 1 pin at a time remove the pin from the ECM connector and install it in its new home in the PCM connector. Use the terminal removal tool so that you don’t damage the terminal.  Take your time and double check what you are doing, you do not want to try and figure this out later if you screw it up.

Don’t forget to run the 4 new wires from the PCM down to the Park/Neutral Switch on the side of the transmission.

Also the are other things listed in the table to explain where you can add some of the new functions that the PCM has compared to your old ECM.  The first one that I have in there now is the TOW/HAUL mode toggle switch, which eventually I will explain on the transmission page.

Once you have all the pins into the new connector, clean everything up and install the covers and any protective wire loom.

 

STEP 3

Plug your newly finished connector from step 2 into your new PCM from step 1.

Secure the PCM to the truck using the existing ECM mounts.

Thanks to all the guys at FSC (NODIH, durbo.jones, 99Chevy7.4L, Pauly) and to Lextech for creating the conversion spreadsheets.

To take this modification even further click here to continue on to Page 3 which is all about switching from the distributor style ignition to the Coil Near Plug (CNP) style ignition that is found on the 98-01 L21 version of the Vortec 454.