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MS3Pro Ultimate by AMP EFI

GM LS 24x Plug and Play Engine Harness – for MS3Pro Ultimate/Evo

4 out of 5 based on 1 customer rating
(1 customer review )
GM LS 24x Plug and Play Engine Harness - for MS3Pro Ultimate/Evo

From: $799.00


Injector Style

MS3Pro ULTIMATE Center Harness – optional

required for ULTIMATE only (not used on EVO)

Alternator Lead Extension – optional

Seals-It Grommet - 1.00" split – optional

AMP EFI 4L60E CAN Trans Control Module & Subharness – optional

AMP EFI 4L80E CAN Trans Control Module & Subharness – optional


For MS3Pro ULTIMATE/ EVO plug and play installation on GM LS engines with a 24x crank trigger.

The MS3-Pro 24x LS Plug and Play Harness is the highest quality, best value option for LS Motors in the industry today.  Save your hard earned time and money while experiencing the virtually limitless feature set of MS3-Pro Engine Management System.  Simply choose your injector style from the drop down menu!

This harness is designed for MS3Pro ULTIMATE/ EVO ECU’s Only.

*ULTIMATE requires a 3rd Black Center Harness , EVO does not.

The MS3-Pro LSX Series plug and play harness is professionally engineered and easy to install.  Fire up your engine on day one!   All wiring is composed of TechFlex woven, self-extinguishing wrapped hi-temp TXL & GXL automotive grade wire with OEM Delphi & TE connectors. Reach the battery under the hood or in the trunk with 4 gauge power & 10 gauge ground wires.  All relays and fusing live in a single, waterproof fusebox and the fuel pump wiring / relays / fusing is big enough for pumps that can handle 1000whp or more right out of the box (10ga wire, 30amp circuit).  Additionally, all of the available I/O of the MS3-Pro are brought out in the harness to make expansion as easy as possible regardless of the featureset you’re planning to use, allowing for killer features like traction control, bump box, table switching, flex fuel, and more.  This harness was designed with room to grow!  And did we mention it’s show-quality-drop-dead-gorgeous?

This harness also is designed for optional automatic transmission control using our MicroSquirt transmission controller (sold separately).  Literally just plug in our transmission controller using the proper sub-harness (for 4L60E or 4L80E) and you’re ready to control your trans!

Required connections:
Constant Power
Constant Ground
Switched Power
Alternator light

Suggested extra connections:
Fuel Pump Power
Tachometer Signal

Note that the alternator connection is designed for high mount alternators such as Corvette and truck setups. Low mount alternator setups such as Camaro, Firebird, CTS-V, and GTO accessory brackets, as well as other aftermarket accessory drives that do not have the alternator high on the driver’s side, require our alternator extension cable.

*All parts are sold for OFF ROAD RACE-ONLY, ground-vehicle use only. Aftermarket EFI/EMS systems are not for sale or use on pollution controlled vehicles. Alteration of emission related components constitutes tampering under the US EPA guidelines and can lead to substantial fines and penalties. Your state/district may also have specific rules restricting your tampering with your vehicle’s emissions system. In short, as stated before, our official policy has to be RACE or OFFROAD USE-ONLY in ground based vehicles ONLY.

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1 review for GM LS 24x Plug and Play Engine Harness – for MS3Pro Ultimate/Evo

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    MS3Pro EVO LS 24X Base Tune [MSQ]

    MS3Pro ULTIMATE 24X-5.7-LS1cam BASE TUNE [MSQ]

    Drivers for the USB connection can be found on the FTDI website

    For the latest MS3Pro firmware, tuning software, complete documentation and base tunes, please visit

    What size screws do I need for the fuse box mounting?

    • It uses #10-32 mounting screws.

    Does this harness have the MS3Pro controlling the alternator?

    • No. You will need to wire the alternator to the charge lamp. That will activate the alternator. See details in the manual.

    Questions & Answers

    1. 0 votes

      To use this harness with an MS3Pro Gen 1, you'll just need to splice the RS232 and USB connectors into the Spare harness trunk.

    2. 0 votes

      This is just the harness. We have a separate entry for an ECU and harness combination.