What counts as a Gen IV LS?
GM's fourth-generation small block covers a big family of V8s, from the 6.0L truck and Commodore engines to the supercharged 6.2L units. Throughout this page we use the LS2 as the reference engine and call out the LS3 where it's different. Most of what follows applies across the family because the sensors, coils and trigger system are shared.
| Spec | LS2 | LS3 |
|---|---|---|
| Layout | 90-degree V8, aluminum block (iron on the LQ9 and LSX) | |
| Displacement | 364 ci (5967 cc) | 376 ci (6162 cc) |
| Firing order | 1-8-7-2-6-5-4-3, with the odd cylinders (1, 3, 5, 7) on the right-hand bank | |
| Stock injectors | About 350 cc/min | About 420 cc/min |
The variants you'll run into
- LS2: 6.0L, 10.9:1, cathedral port heads.
- LS3: 6.2L, 10.7:1, rectangular port heads that flow better than the cathedral design.
- L76: the Australian 6.0L with rectangular ports and GM's cylinder deactivation (DOD) hardware.
- L98: 6.0L with rectangular ports and a very mild camshaft.
- LS7: 7.0L, dry sump, steel crank and titanium rods.
- LSA and LS9: supercharged 6.2L engines at 9.0:1 and 9.1:1, with the LS9 carrying the bigger blower.
- LQ9: 6.0L iron-block truck engine at 10.0:1.
- LSX: GM's heavy-duty iron 6.0L block with thicker cylinder walls, an extra head bolt per cylinder, better main bearing oiling and doweled six-bolt mains.
Trigger system: 58x crank and 4x cam
The crank wheel on a Gen IV has a 60-2 pattern: sixty tooth positions with two left out. You'll hear it called "58x" in the LS world. The ECU uses that gap to find its place, then times the engine from the first tooth after the gap rather than from the gap itself. The cam gear carries a 4x pattern made of two short and two long teeth.
This was a real step forward from the Gen III 24x wheel. Big cams on a Gen III can push the cam edge around enough to cause edge-swap problems, and the missing-tooth crank wheel largely avoids that. If the cam signal is lost, the ECU can still half-sync on the crank wheel and keep the engine running, which is useful redundancy. Our full LS2-LS3 trigger setup guide walks through the ECU settings.
Crank sensor
The crank sensor sits above the starter at the back of the block. Despite what many people call it, the Gen IV sensor is a normal Hall effect unit. The quickest way to tell generations apart is color: Gen IV sensors are grey, Gen III sensors are black. A black Gen III sensor is a reluctor with built-in signal conditioning, and it won't read a Gen IV wheel.
| Sensor pin | Job | Haltech trigger cable |
|---|---|---|
| A | Signal out | Yellow wire, Trigger + |
| B | Ground | Blue wire, signal ground |
| C | Power | Red wire, 12V+ |
Cam sensor
On Gen IV engines the cam sensor lives in the timing cover at the front of the engine, and some vehicles add a short extension lead. It's also a Hall effect sensor, and its signal goes to the ECU's Home input. Check the pin assignment against your harness documentation before you connect it.
Mixing Gen III and Gen IV parts
Swapped and custom-built engines often end up with a mix of parts. Three of the four crank and cam combinations can be made to work. One can't.
| Crank wheel | Cam pattern | Trigger type to select | Works? |
|---|---|---|---|
| Gen III 24x | Gen III 1x | General Motors - LSx Gen III (24x + 1x) | Yes |
| Gen III 24x | Gen IV 4x | None available | No |
| Gen IV 58x | Gen III 1x | Generic Missing Tooth Single Tooth Home, crank-mounted, 60 teeth, 2 missing | Yes |
| Gen IV 58x | Gen IV 4x | General Motors - LSx Gen IV (58x + 4x) | Yes |
If you're still planning the build, we'd choose the Gen IV crank and cam every time. It tolerates much more cam timing movement before edges get too close, syncs faster, starts quicker and gives you that crank-only fallback.
Ignition: coil wiring and dwell
Gen IV engines are coil-on-plug, with one coil per cylinder mounted on the valve covers. The coils have built-in igniters, so they wire straight to the ECU's ignition outputs with no external igniter. You'll see two versions: the standard coil and the truck coil, which has a large finned heat sink. Both use the same wiring. The pin letters are molded into the connector shell.
| Coil pin | Connects to |
|---|---|
| A | Ground, to the cylinder head |
| B | Ground (ECU signal ground on paper, but see the tip below) |
| C | ECU ignition output |
| D | 12V+ |
Ground both A and B to the cylinder head. Poor coil grounding is a known way to kill LS coils. In the software, set the ignition to Constant Charge with a Falling edge. Running these coils on a rising edge will damage them.
Dwell needs care too. Charge an LS coil for much more than about 5 ms and it can fire on its own, which shows up as random, wandering timing. The catch is that it often idles and cruises fine, then misbehaves as rpm climbs because the gap between firing events gets shorter. Keep dwell sensible, especially up top, and check the LS2 ignition coil page for more detail.
There are also no factory timing marks on an LS. Before you trust your timing light, find true TDC with a piston stop and make your own mark.
Fuel system
Every Gen IV runs sequential port injection with high-impedance injectors aimed at the back of the intake valve. The factory fuel system is returnless at a fixed pressure, so the rail pressure doesn't follow manifold pressure. If you keep it that way, your injector data needs to account for changing pressure differential across the injector as boost or vacuum changes.
Throttle: drive by wire or cable
Most Gen IV engines use a single drive-by-wire throttle body. Controlling it takes an Elite 1500 or Elite 2500, since those are the Elite models with DBW control. Our Elite 2500 Gen IV DBW-ready terminated harness kit is the simplest way to get there.
| Throttle body pin | Goes to | What it carries |
|---|---|---|
| A | DBW 1 | Motor power, side one |
| B | DBW 2 | Motor power, side two |
| C | Signal ground | Sensor ground |
| D | AVI 2 | First throttle position signal |
| E | 5V+ | Sensor supply |
| F | AVI 3 | Second throttle position signal |
| Pedal pin | Function | Haltech connection |
|---|---|---|
| 1 and 2 | 5V supply | 5V+ |
| 3 | Pedal signal 1 | AVI 4 |
| 4 and 5 | Ground | Signal ground |
| 6 | Pedal signal 2 | AVI 5 |
A cable throttle works fine too. Its three-wire TPS takes 5V+ on pin A, signal ground on pin B and sends its signal from pin C to a spare AVI. For that setup, look at the Elite 2500 Gen IV non-DBW harness kit.
Idle control
On DBW engines the throttle body handles idle. Cable-throttle engines use a stepper idle air valve, which needs an Elite 1000 or higher. The Elite 550, 750 and 950 can't drive it. Wire valve pins A through D to Stepper 4, 3, 2 and 1 in that order, then set the drive type to Both, steps to 240 and speed to 75. The idle control guide covers tuning from there.
Sensors: what to keep and how to wire them
| Sensor | Where it is | Wiring and calibration |
|---|---|---|
| MAP | Intake manifold | Pin 1 5V+, pin 2 signal ground, pin 3 to an AVI. GM used 1.0, 1.3 and 2.0 bar units depending on model, and ESP includes calibrations for most. The LS3 sensor is part number 0 261 230 282, a 1.3 bar part. |
| Coolant temp | Left-hand head, near the number 2 exhaust port | Two wires, either way around. Load "Temperature - Holden VP V8 Coolant Sensor.cal". |
| Air temp | Built into the MAF | Load "Temperature - Holden VP V8 Air Sensor.cal". Both temperature calibrations assume the ECU's 1k pullup to 5V. |
| Oil pressure | Oil filter housing | A to signal ground, B to 5V+, C to an AVI. The matching calibration file is "Oil Pressure - GM LS1 Stock Sensor.cal" (0.5 V is 0 psi, 4.5 V is 130 psi). Harness colors vary by market. |
| Knock | One per bank, outside of the block | Two non-resonant sensors that the Haltech can use directly. |
| MAF | Intake tract | Usually removed on a Haltech install, but it can stay. A signal to a spare AVI, B 12V+, C and E to signal ground, D (air temp) to a spare AVI, AVI 7 being typical. |
The coolant sensor uses a Delphi connector where the wire goes through the housing before you crimp the terminal, and then the terminal is pulled back to lock. Get the order wrong and you'll be cutting it off to start again.
O2 sensors
Stock Gen IV engines carry four narrowband sensors. We strongly recommend replacing the two front sensors with a proper wideband, such as the Haltech WB2 dual channel kit. If you do keep a narrowband, its black wire is the signal (not ground), the grey goes to signal ground, and the two white heater wires go to switched 12V and chassis ground in either order. The heater ground can be switched by an injector, stepper or DPO output, but never by an ignition output.
Transmission: 6L80E
The GM 6L80E six-speed automatic that often comes behind these engines needs a controller talking to it over CAN. It's GM-built and is described as sharing its design with the ZF 6HP, with different gearing. Talk to us about the Nexus TI6L interface if you're keeping the auto.
Troubleshooting common Gen IV faults
| Symptom | Usually |
|---|---|
| Engine position errors after a cam swap | The cam edge now sits too close to a crank tooth edge and swaps sides. Watch the Home Percentage of Valid Travel channel; readings near 0% or 100% are the danger zone. Try the other cam edge (change TDC offset by 360, keeping it within 0 to 720) or add Home filtering of 2 or 3. The Home % reading rises with rpm, so check it high in the rev range. |
| No crank signal at all | Wrong sensor. A black Gen III sensor on a Gen IV wheel won't work; sensor type and wheel must match. |
| Random timing or misfire at high rpm only | Dwell too long for the coils, or a poor coil ground |
| Dead coils after first start | Rising edge selected, or coils not grounded to the head |
| Can't control idle on a cable-throttle engine | Stepper idle valve on an Elite 550, 750 or 950, which don't support it |
LS2 / LS3 FAQ
Can I use my Gen III crank sensor on a Gen IV engine?
No. The black Gen III sensor is built for the 24x wheel and won't produce a usable signal from the 58x wheel. Use the grey Gen IV sensor.
Do I need the MAF with a Haltech?
No. Most installs run speed density off the MAP sensor and remove the MAF. If you do that, you still need an air temperature sensor somewhere in the intake, because the factory one is inside the MAF.
Which Haltech runs a DBW LS3?
For the Elite range, the Elite 1500 and 2500 control drive-by-wire. Check the LS terminated harness guide, or book a free consultation and we'll match an ECU and harness to your build. For the older engine, see our LS1 Gen III page.
