LS Swaps Are Brilliant — Until You Get to the Wiring

The LS engine family is one of the greatest performance bargains in automotive history. Cheap, abundant, incredibly powerful, and with an enormous aftermarket — it's no wonder LS swaps have taken over the performance scene in New Zealand and worldwide.

But ask anyone who's done one: the wiring is where most builds stall. The factory LS harness is designed for a specific vehicle with specific systems. Drop that engine into a different chassis and you're suddenly dealing with a tangle of wires that don't belong, missing sensors, and an ECU that doesn't know what car it's in.

At Turner Auto, we've wired more LS swaps than we can count. This guide covers everything you need to know to get your LS1 or LS2 wired up properly.

Your Three Harness Options

1. Modify the Factory Harness

The most budget-friendly option is to take the original LS harness and strip it back — removing all the body-related wiring and keeping only what the engine needs. This works, but it's time-consuming and requires solid electrical knowledge. One wrong cut and you'll spend hours troubleshooting.

2. Buy a Pre-Made Conversion Harness

Several companies make LS swap harnesses designed to work with a standalone ECU. These are a good middle ground — cleaner than a modified factory harness and less expensive than a full custom build. Quality varies significantly between brands, so choose carefully.

3. Custom Built Harness

For serious builds — especially motorsport, drift, or track cars — a fully custom harness is the gold standard. Built to your exact specifications, routed perfectly for your chassis, with quality connectors and correct wire gauges throughout. This is what we build at Turner Auto for customers who want it done right.

Choosing Your ECU for an LS Swap

The factory LS ECU (PCM) can be used with the right tuning software, but most performance builders opt for an aftermarket ECU for better tunability and features. We work with all the leading platforms and can recommend the right one for your build:

• MaxxEcu — Excellent LS support, great software & transmission control Browse MaxxEcu →
• ECU Master — A capable, cost-effective alternative with solid LS compatibility. Browse ECU Master →
• Link ECU — A New Zealand-made ECU with a strong reputation and excellent LS support. Browse Link ECU →
• Haltech — An Australian-engineered platform with a long motorsport pedigree and comprehensive LS compatibility. Browse Haltech →

Read our full MaxxEcu vs ECU Master comparison or our NZ ECU Buyer's Guide to help decide.

Essential Sensors for Your LS Swap

A standalone ECU needs to read a full suite of sensors to run your LS correctly. Here's what you'll need:

• Coolant Temperature Sensor (CTS) — LS engines use a specific GM sensor; confirm compatibility with your ECU
• Intake Air Temperature (IAT) — Usually integrated into the MAF or intake manifold
• Manifold Absolute Pressure (MAP) — Critical for speed-density tuning (common on LS builds running without a MAF)
• Throttle Position Sensor (TPS) — Factory LS TPS works well with most aftermarket ECUs
• Wideband O2 Sensor — Essential for tuning; don't skimp here
• Knock Sensors — The LS uses two knock sensors; both must be wired correctly
• Cam and Crank Position Sensors — Factory sensors are reliable; keep them

We stock a full range of sensors and connectors for LS builds. Browse our Sensors & Connectors range →

Common LS Wiring Mistakes to Avoid

Ignoring the Knock Sensor Wiring

The LS knock sensors use a specific shielded cable. Run them with standard wire and you'll get false knock readings that pull timing and kill power. Always use shielded cable and connect the shield at one end only.

Skipping the Dedicated Ground Points

LS engines need solid, dedicated ground points — one at the block, one at the head, and a sensor ground back to the ECU. Poor grounds cause all manner of strange faults and sensor errors.

Using Undersized Wire on Injectors and Coils

The LS runs eight injectors and eight coils. These are high-current circuits. Undersized wire causes voltage drop, heat, and unreliable firing. Use the correct gauge throughout.

Not Planning for the Alternator and Starter

Your LS swap needs a properly rated alternator and starter for the new chassis. We stock quality starter motors suited to LS applications — don't overlook this part of the build.

LS Parts at Turner Auto

We stock a dedicated range of parts to support your LS swap, including sensors, connectors, ECU mounts, and more. Browse our full LS1 LS2 parts range →

Need Professional LS Wiring in Auckland?

If you'd rather have it done right the first time, our team handles LS swap wiring from start to finish — custom harness build, ECU installation, and configuration. We're based in Auckland and work on builds from across New Zealand.

Get in touch to discuss your LS build →

Also read: ECU Wiring Auckland: What You Need to Know Before Your Build