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LS swap ECU comparison: Holley vs Haltech vs MaxxECU vs factory PCM

Every LS swap needs a computer. You can reuse a GM computer with a standalone harness, buy a complete EFI kit, or run a full standalone ECU. The big questions are price, drive-by-wire support and whether it can shift your automatic.

Compared

Prices change often; check current pricing before you buy. "Not listed" means the maker's page didn't say.

Three ways to run an LS

What each option includes

• Speartech LS 58x harness + programmed PCM: Standalone harness plus a GM PCM programmed for your combo. Uses GM's own computer; later tuning is HP Tuners/EFILive work.
• Holley Terminator X LS kit: ECU + LS main harness + handheld or USB/CAN cable (24x or 58x). Kits come with a touchscreen handheld, or a USB/CAN cable (T versions) for laptop tuning.
• PSI Conversion Classic LS kit: Standalone harness + engine controller kit (Gen IV 58x). Factory-computer route like Speartech.
• Holley Terminator X Max LS kit: Terminator X with drive-by-wire and transmission control. Holley's Terminator X version with drive-by-wire and 4L-series transmission control.
• Haltech Nexus Rebel LS: ECU + terminated LS harness (Gen III or Gen IV DBW kit). Manual-trans kit as sold; add the Ti4L module to run a 4L-series automatic.
• FiTech Ultimate LS 500 HP w/ trans control (70007): EFI system with long-runner cathedral intake and transmission control (per the product title). Comes with the intake manifold, so it replaces your top end as well as the computer.
• Haltech Elite 2500 LS kit: Elite 2500 ECU + terminated Gen IV LS harness, DBW ready. Gen III version of this kit is discontinued.
• MaxxECU RACE LS kit: RACE ECU + terminated GM LS Gen III/IV harness. Sold mainly through dealers; price is from MaxxECU's own store.

What the sources say, by brand

Holley

• The 24x main engine harness for LS1-style engines is Holley 558-102 and the 58x harness for LS2/3/7 engines is 558-103.
• The X Max 4L60E/4L80E transmission harness is Holley 558-405; drive-by-wire harnesses are 558-406 (GM LS) and 558-429 (early truck).
• Holley's official manual defines the MPFI Terminator X kits as designed for stock and mild-cam, naturally aspirated LS engines; Holley publishes no kit-level 'supports up to X hp' rating for these MPFI LS kits.
• The Holley Dominator EFI ECU has integrated drive-by-wire throttle body control for up to two DBW throttle bodies (GM, Chrysler, Ford, Nissan compatible).
• The Holley Dominator EFI ECU has integrated electronic transmission control for GM 4L60E and 4L80E transmissions (plus Ford AODE/4R70W).
• Holley Terminator X LS systems are designed to use a Bosch LSU 4.9 wideband oxygen sensor supplied by Holley (service part number 554-155).
• The base Terminator X ECU is Holley service part 554-152 and the Terminator X Max ECU is 554-153.
• Terminator X injector harnesses are Holley 558-200 for EV1, 558-201 for EV6, and 558-214 for truck/Multec applications.

Haltech

• Haltech's Elite 2500 LS1/LS6 terminated harness HT-141362 suits factory EV1 injector connectors and common US-style Delco/Bosch GM alternator connectors.
• Haltech's Elite 2500 LS1/LS6 terminated harness HT-141362 is pre-wired to connect directly to the OEM 7-pin coil harness connector.
• Haltech's HT-141362 Elite 2500 LS1/LS6 harness supports retrofit of a Gen IV LS2/LS3 drive-by-wire throttle body.
• Haltech's Elite 2500 LS1/LS6 terminated harness HT-141362 is manual-transmission only.
• The Haltech Nexus R3 VCU includes 1 on-board wideband controller supporting NTK and LSU 4.9 sensors.
• Haltech's Nexus R5 VCU + LSx DBW terminated harness kit, part HT-195405, uses EV6 primary injector plugs and requires the OEM ignition sub-harness.
• The Haltech Nexus R5 VCU includes 2 on-board wideband controllers supporting NTK and LSU 4.9 sensors.
• Haltech lists automatic transmission control for GM 4L60E and GM 4L80E on the Nexus R5 VCU.

FiTech

• FiTech's transmission-control Ultimate LS kits include built-in control for GM 4L60, 4L65, 4L70, and 4L80 automatic transmissions.
• FiTech's generic marketing copy says its EFI systems work on engines 'reaching up to 1200 horsepower,' but the Ultimate LS kit on that page is the 500 HP version — the 1200 HP figure describes FiTech's throttle-body EFI line, not an Ultimate LS kit.

AEM

• AEM's 30-3821 Infinity layover harness is designed for GM LS 24x-reluctor engines with manual transmissions.
• The Infinity ECU is sold separately from the 30-3821 harness, and AEM supplies base configuration files for GM LS 24x engines.
• AEM's 24x LSX layover harness pinout (36-3821) is drawn specifically for the Infinity 508.
• For 58x GM LS engines, AEM's Infinity wizard specifies trigger offset 0.0 deg BTDC, cam-sync adjustment 106.0, and spark delay compensation 1000 us/10.
• AEM's Infinity LSX sensor wizard lists the GM LS2 1-bar MAP sensor, part number 9359409.
• AEM specifies its GM LS 24x layover harness for manual transmissions; no AEM Infinity feature list found documents internal automatic-transmission (4L60E/4L80E/6L80E) control.
• For 24x GM LS engines, AEM's Infinity wizard specifies trigger offset 9.0 deg BTDC, cam-sync adjustment 0.0, and spark delay compensation 1500 us/10.
• AEM offers the 30-3702 mini lead harness with a fused power distribution center and main relay for custom Infinity harness builds.

MS3Pro

• The MS3Pro EVO communicates over RS232, USB 2.0, and CAN.
• The MS3Pro EVO uses a sealed high-temperature nylon case with heavy-duty AMPSEAL connectors, forming a sealed enclosure that protects the internals from the elements.
• The MS3Pro family has no onboard wideband controller; a wideband installation requires a separate wideband controller or gauge providing a 5V analog output.
• The MS3Pro Mini can accept wideband oxygen sensor data over the CAN bus where the wideband controller supports it, in addition to the 0-5V analog input.
• The MS3Pro EVO's internal SD-card data logging captures up to 64 channels at 330 Hz.
• The MS3Pro Mini package supports drive-by-wire only through the external AMP Drive-By-Wire Controller, not natively.

FuelTech

• The LS550 harness includes wiring for 2 FuelTech Peak and Hold drivers for use with low-impedance (peak and hold) injectors; high-impedance injectors run direct.
• The LS550 harness is set up for two FuelTech WB-O2 Nano O2 conditioners and two Bosch LSU 4.2 wideband O2 sensors.
• The FuelTech FT450 ECU (touchscreen, without harness) carries FuelTech part number 3010005384.
• The FuelTech FT550 EFI system (without harness) carries FuelTech part number 3010005496.
• The FuelTech FT600 EFI system (without harness) carries FuelTech part number 3010004009.
• Retailer spec card for the FuelTech FT550 (part 3010005496) lists Transmission Control: No.

FAST

• LS coil-near-plug installations pair the XFI 2.0 with the separate FAST XIM ignition module (module-only part 305008), which interfaces the XFI system to distributor-less ignitions including Gen III/LS.
• The FAST EZ-TCU automatic transmission controller supports the GM 4L60E, 4L65E, 4L70E, 4L80E, and 4L85E as well as the TCI 6x six-speed transmission.
• The core XFI 2.0 ECU kit carries FAST part number 301000.
• The multi-port XFI Sportsman EFI system carries FAST part number 303000.
• FAST positioned the XFI Sportsman to fill the gap between the plug-and-play EZ-EFI systems and the hardcore-racing XFI controller, targeting muscle cars, bracket racers, late models, and junkyard swaps.
• The 4150-style eight-injector throttle-body XFI Sportsman kit is rated to 1,200 hp (FAST does not state crank vs wheel); no horsepower ceiling is published for the standalone Sportsman ECU or multi-port system itself.
• FAST's XIM ignition module sold without a harness is part number 305008.

BigStuff3

• The BigStuff3 transmission-control wire harness connects directly to the stock GM transmission input and output shaft speed sensors (TISS/TOSS) and the stock 20-pin header connector, using 5 connections total.
• BigStuff3 GEN3 PRO SEFI part number BS3-004-002 ships with a powder-coated aluminum ECU, main wire harness, injector harness, wide-band oxygen sensor, and communication cable, and that part number adds DAI internal data logging.
• BigStuff3 announced a new four-stage dry nitrous oxide system for GEN3 available in February 2011.
• 4L60E transmissions only have a TOSS (output shaft speed) sensor, with no TISS input-sensor connection needed on the BigStuff3 transmission harness.
• BigStuff3 recommends pressure sensor part number JMI-003-014 (1/8-inch pipe thread, 0-150 psi) for logging fuel pressure, oil pressure, and turbo back pressure with the DAE external-logging option.

ECUmaster

• The ECUmaster EMU Black is a universal spark-ignition engine control computer and the successor to the original ECUmaster EMU.
• ECUmaster USA's EMU Black product page lists 8 injector outputs, contradicting the current official manual's specification of 6.
• ECUmaster USA's SKU for the EMU Black standalone ECU is ECUEMUBLK.

Link

• Link offers a Gen 4 drive-by-wire LS V8 bundle covering LS2, LS3, LS7 and LSA engines.
• Link's terminated LS harness ships with PCLink base maps in four combinations: Gen 3 or Gen 4 crossed with DBW or cable throttle.
• Link's terminated GM LS Gen 3/4 engine harness part number is 101-0300.
• The Link G4X XtremeX part number is 109-4000 and it provides 8 injector drives and 8 ignition drives.
• The Link G4X XtremeX includes 512 MB of onboard data logging.
• The XtremeX has no onboard digital wideband lambda control; for that requirement Link points buyers to the Fury.
• The Link G4X StormX part number is 108-4000 with 8 injector and 8 ignition drives, positioned below the XtremeX.
• Link lists fully programmable e-throttle control among advanced features not found on the Storm, indicating the StormX lacks integrated DBW.

MSD

• MSD part number 2900 is the Atomic EFI throttle-body (TBI) master kit — a square-bore carburetor replacement — not an Atomic LS kit.
• MSD rates the Atomic LS master kit for engines up to 1,000 horsepower.
• MSD's current Atomic LS 2950 retail listing states the system accepts both mechanical and electronic throttle control systems.
• MSD does not build transmission control into Atomic LS EFI kits; running an electronic automatic (4L60E/4L65E/4L70E/4L80E/4L85E) requires the separate Atomic Transmission Control Module, PN 2760, plus an application-specific harness.

PSI

• The Terminator X system requires a fuel pump capable of supplying 255 liters/hour or 400 lb/hr of fuel at the system's 60 PSI requirement.
• BigStuff3 recommends pressure sensor part number JMI-003-014 (1/8-inch pipe thread, 0-150 psi) for logging fuel pressure, oil pressure, and turbo back pressure with the DAE external-logging option.

Wiring references

• Holley Terminator X / HP / Dominator pinout
• Drive-by-wire pedal & throttle body pinout
• Speartech harness wiring
• Painless 60522 wiring

ECU questions

• Stock PCM vs Holley Terminator X for an LS swap
• How to make a standalone LS wiring harness
• Is switching from a PSI harness and stock ECU to a Holley Terminator Max worth it?
• Why does the LS ECU need a VSS signal if I keep my old mechanical-speedo transmission?
• How should electric fans be wired with a Terminator X / LS swap ECU?
• Where should I run a standalone LS harness into the cab of a 72 without drilling new firewall holes?
• Which factory wire do I tap for the ignition feed on a PSI standalone harness in a 1967 C10?
• Which standalone harness company should a first-timer use for a 5.3 DBW / 4L60E swap in a 67 stepside?
• Can I mate a T56 to an LM7 that was originally behind an automatic, and will the ECU complain?
• Standalone trans cooler vs radiator cooler: which way keeps an automatic alive?
• What wiring should I plan for a Holley Terminator X on a C3 LS swap?
• Is Holley Terminator X worth $1,000 over a factory ECM and harness for an LS swap?
• What's the best wiring approach for an LM7 LS swap: stripped stock harness with stock ECM and fuse block, full standalone harness, aftermarket harness with stock ECU, or a standalone ECU?
• Should I use an aftermarket ECU or the factory computer for a budget LS swap, and how do I delete VATS cheaply?
• Can I DIY a standalone harness from a Gen IV E38 ECU for an LH6 5.3 swap, and how do VATS delete and speedo calibration work?

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