You've got the engine in, the harness sorted and the fuel system plumbed. Now you need a computer that actually knows what it's running. That's where a lot of LS swaps stall out, sometimes literally.

A stock GM PCM pulled from a donor truck is calibrated for that truck, with its transmission, its tire size, its security system and its factory parts. Drop it into a swap untouched and you'll often fight VATS no-starts, the wrong transmission settings, a speedometer that's way off, and trouble codes for parts that aren't even on the vehicle anymore. If the engine has a cam or bigger injectors, the stock calibration gets even further from what the combination needs.

Midgard Industries' mail-in LS swap startup tune fixes that. You send in your GM P01 or P59 PCM, and it's programmed around the information you provide about your build, then shipped back ready to install.

What's included in the $100 stock / near-stock package

This package is built for stock or mildly modified Gen 3 LS swaps that need the PCM configured to work correctly in the new vehicle. It can include:

  • VATS / security removal
  • Correct engine displacement
  • Automatic or manual transmission setup
  • 4L60E or 4L80E configuration
  • Electric fan control
  • MAP sensor setup
  • Tire size, rear gear and speedometer correction
  • Power enrichment and torque management adjustments
  • Startup / base calibration
  • Swap-related diagnostic code changes for components no longer used

What the $150 cammed / modified package adds

If you're running an aftermarket cam, larger injectors, a different intake or throttle body, or you've swapped in a 4L80E or manual transmission, the cammed package includes everything above, plus:

  • Injector flow-rate setup
  • A camshaft-based VE starting calibration
  • Increased or adjusted idle airflow
  • Camshaft idle settings
  • Startup fueling changes
  • Additional startup and drivability calibration for your combination

It's much more than simply turning off VATS. The goal is a calibration that starts, idles and drives as close to right as possible from the first key turn.

Which PCMs are supported?

The service covers customer-supplied GM P01 and P59 PCMs used on Gen 3 LS engines. The easiest way to tell them apart is the connector colors:

  • P01: red and blue connectors
  • P59: green and blue connectors

Both drive-by-cable and drive-by-wire swaps are supported, along with 4L60E, 4L80E and manual transmissions. If you're not sure what you have, send a photo of the connectors and the service-number label and I'll help identify it.

What to send with your order

The more accurate your build information, the better the starting calibration can be matched to your combination. Have this ready:

  • Engine size and year
  • PCM service number
  • Transmission type
  • Cam specs, if modified
  • Injector part number or flow rate
  • MAF and MAP sensor information
  • Tire size and rear gear ratio
  • Fuel type
  • Desired fan temperatures
  • A complete modification list

How to order

  1. Order your startup tune online at midgardind.com/ls-swap-base-tune.
  2. Mail your PCM to Midgard Industries along with your build information.
  3. Your PCM is programmed for your combination and shipped back. Return shipping is $10, and local drop-off is available in Longview, Texas.

Want to double-check compatibility first? Message me with your engine, cam, transmission and PCM connector colors, and I'll confirm before you order.

A note on startup tunes

A startup / base calibration is designed to get your swap running and give you a solid starting point. It isn't a replacement for final dyno or street tuning. Cammed and heavily modified combinations should still be verified and fine-tuned using scanner data, preferably with a wideband O2 sensor. When you're ready for that, Midgard Industries also offers complete custom EFI tuning, locally or remotely.

Emissions-related modifications are available only for legal off-road or competition applications.

Ready to get your swap running right? Order your mail-in LS swap startup tune here.