Overview

The Rebel LS ECU is one of Haltech’s advanced engine control units in the Nexus range, offering additional functionality beyond simply controlling your GM Gen III or Gen IV LS engine. It functions not only as an engine control unit but also as a wideband O2 controller, a data logger, and a Wi-Fi module, all integrated into a single unit. With its innovative and user-friendly technology, the Rebel LS ECU sets a new standard in the market for LS engine management. Paired with a Nexus Rebel LS terminated harness, it provides a comprehensive range of performance and tuning capabilities for GM LS engines.

Rebel LS kits - what's included?

Currently, there are two Nexus Rebel LS kits available from Haltech. These include:

HT-220201 - Nexus Rebel LS kit to suit a Gen III LS engine with cable throttle, EV1 injector plugs, and a manual transmission

1. Nexus Rebel LS ECU (HT-220001)
2. Nexus Rebel LS main terminated harness (HT-186500)
3. Throttle sub-harness to connect to cable throttle setup TPS + IAC (HT-186504)
4. Injector sub-harness with EV1 connectors (HT-186501)
5. T56 manual transmission harness (HT-187003)
6. Bosch LSU 4.9 wideband O2 sensor and bung
   
7. Air temperature sensor and bung
   
8. Alternator adapter harness set
   
9. Gen III knock sensor adapter harness (HT-186508)
   

HT-220204 - Nexus Rebel LS kit to suit a Gen IV LS engine with a 6-pin electronic throttle, EV6 injector plugs, and a manual transmission

1. Nexus Rebel LS ECU (HT-220001)
2. Nexus Rebel LS main terminated harness (HT-186500)
   
3. Electronic throttle sub-harness to connect to a standard GM 6-pin Drive-By-Wire throttle (HT-186505)
4. Accelerator Pedal Position adapter harness to suit a Corvette Pedal (HT-186507)
5. Injector sub-harness with EV6 connectors (HT-186502)
6. T56 manual transmission harness (HT-187003)
7. Bosch LSU 4.9 wideband O2 sensor and bung
   
8. Air temperature sensor and bung
   
9. Alternator adapter harness set
   
10. Gen IV MAP sensor adapter harness (HT-186511)
11. Gen IV Oil pressure sensor adapter harness (HT-186510)

Rebel LS optional accessories

These optional accessories can be purchased separately:

1. HT-186503 - Nexus Rebel LS - Multec 2 injector sub-harness
   
2. HT-186506 - Nexus Rebel LS - 8 pin DBW adapter harness
   
3. HT-186512 - Nexus Rebel LS - Bosch pedal adapter harness
   
4. HT-011900 - Bosch pedal assembly 
5. HT-011000 - Flex fuel composition sensor
   
6. HT-010904 - 150 psi "TI" fuel/oil pressure sensor
   
7. HT-020400 - 3 port boost control solenoid
   
8. HT-159976 - WB1 single channel CAN wideband O2 controller kit - suits Bosch LSU 4.9 sensor
   
9. HT-159986 - WB2 dual channel CAN wideband O2 controller kit - suits Bosch LSU 4.9 sensor

Rebel LS Installation

General installation warning

1. The Nexus Rebel LS ECU allows connection to your laptop via the Nexus Software Programmer (NSP) using the supplied USB cable, without the need for +12V power. This feature conveniently lets you set up your ignition, injector, and various other outputs before initially powering up the control unit using the supplied harness. Turning on the ECU with incorrect configurations can lead to damage to both the engine and ECU components.
   
2. The wiring harness is not designed to provide grounding for your engine. Ensure your engine is adequately grounded using a grounding or earthing strap to connect your engine to the battery.
3. Avoid creating sparks or using electrical devices near flammable substances.
4. Always disconnect the battery cables when working on the electrical systems of your vehicle.
   
5. Make sure all fuel system components and wiring are installed away from heat sources, properly shielded if necessary, and in well-ventilated areas.
   
6. After installation, double-check for any fuel leaks and ensure that no wiring is left exposed or uninsulated to avoid the risk of a fire from a spark or short circuit.
7. Do not charge or disconnect the battery while the engine is running. Doing so could expose the control unit to an unregulated power supply, which might lead to control unit failure.

Essential tools for installation

1. A laptop (to install the NSP software to configure the ECU)
   
2. Wire stripper and crimping tools
   
3. Battery cable crimp tool (4AWG)
   
4. Cable ties
5. Digital multi-meter
   
6. Wrench set
   
7. Drill and hole saw (51mm / 2") - to run the harness inside the cabin (depends on ECU installation location)
   
8. Step drill bits and welding tools - O2 sensor bung installation

ECU location and harness layout

Battery connection

ECU connectors (Plugs A, C, and E)

Ignition switch input

The ignition switch input (pink) wire must be connected to a switched +12V source to turn the Nexus Rebel LS ECU on. When connecting this wire to the ignition key switch, it is important to make sure to use the main ignition wire (i.e., not accessory) so it doesn’t lose power when the key is in the “Start” position, causing the ECU to momentarily turn off. The pink wire is the flying lead (unbraided) coming out of the in-cabin inputs and outputs connector branch. 

Ignition coils (Odd and Even banks)

This main terminated harness is designed to plug into the OEM ignition sub-harness and therefore no ignition sub-harness is supplied. Ensure the correct ignition breakout connector is connected to the corresponding ignition coil sub-harness bank on the engine. Refer to the diagram below to identify the odd and even banks on a GM LS engine. 

The harness also includes two 13mm ignition coil ground ring terminals, which need to be bolted onto each of the cylinder heads to provide grounding for the coils. You can use any of the pre-existing holes at the back of the cylinder heads for this purpose.

NOTE: The factory LS ignition coils come with built in igniters. Should you choose to switch to a different kind of ignition coil, it’s crucial to confirm that the new coils also have built-in igniters prior to wiring them to the ignition breakout connectors. Using ignition coils that do not have igniters built-in will damage the ECU.

Fuel Injectors

This Rebel LS terminated harness uses an injector breakout connector to plug into multiple types of injector sub-harnesses. The choice of sub-harness will depend on the type of injector connectors that are used on the engine.  Each injector plug is labeled accordingly to easily identify which injector on the engine it connects to. Refer to the diagram below for LS engine cylinder number identification.

NOTE: The Rebel LS ECU only supports high impedance injectors. 

Throttle connector

Use this connector to plug into a Nexus Rebel LS throttle adapter harness for either electronic or cable throttle applications.  

Accelerator Pedal Position (APP)

Use this connector to connect to a Rebel LS accelerator pedal adapter harness if your application requires Drive-By-Wire (DBW) or Electronic Throttle Control. The adapter harness also includes a wire designed for connection to a brake pedal switch or brake light signal, as part of the DBW control safety strategy. This brake input signal is expected to read +12V whenever the brake pedal is engaged.

Auxiliary 25A output (AX25+)

The Rebel LS ECU provides a user-definable high-current output, capable of supplying +12V with a maximum rating of 25A. This output is connected via the Red/Blue 12AWG cable on the Rebel LS terminated harness, labeled as AX25+. 

Within the software, you can customize this output’s function to control various devices. This includes operating a secondary fuel pump or thermofan, activating a high-current solenoid (e.g., for nitrous or transbrake), or simply serving as a switched +12V supply to power auxiliary devices, vehicle lights, or additional harnesses.

Additionally, this output can be configured to control the starter solenoid if your vehicle doesn’t have a starter signal wire in the body harness. This feature allows the Nexus Rebel LS ECU to inhibit the starter motor from engaging when necessary, such as if the transmission is not in Park or Neutral, or to ensure the brake or clutch pedal is pressed before starting the engine.

Fuel pump

The harness also provides direct fuel pump control using the Red/Yellow 12AWG cable terminated with a butt splice connector. Utilize this cable to supply +12V power directly to the fuel pump, allowing the ECU to prime the pump when the system is turned on and to implement safety functions, such as automatically turning the pump off when the ECU no longer detects an RPM signal.

Fan control

This harness provides direct thermofan control using the Red/Orange 12AWG cable terminated with a butt splice connector. Use this cable to supply +12V power directly to the thermofan and leverage ECU functions, such as setting the fan’s on/off temperature threshold, activating the fan with air-conditioning, or deactivating the fan when the vehicle reaches a specified speed (vehicle speed sensor is required).

Cam sensor

The cam position sensor plug connects directly to the sensor, however, note that the cam sensor wiring varies between models for the GM LS engines. Hence, the plug has the signal wire (yellow) and sensor power wire (red) both unplugged, and is left for the installer to “pin” into the connector to suit what the cam sensor requires. 

Refer to the table below for the pinout. Insert the pins into the connector until they lock into place. Before connecting to the cam sensor, install the wire retainer at the back of the connector.

Crank sensor

The crank position sensor plug connects directly to the engine’s crank angle sensor, which is located behind the starter motor towards the rear of the engine block.

Manifold Absolute Pressure (MAP) sensor

The MAP sensor connector on the harness plugs into a Gen III style sensor as shown below. If you are using a Gen IV MAP sensor from a later model engine, a HT-186511 MAP sensor adapter harness can be used to suit.

Fuel pressure sensor

The Rebel LS main terminated harness comes with an early style 3-pin pressure sensor connector that is compatible with Haltech fuel pressure sensors, should you choose to install one.

The use of a fuel pressure sensor is highly recommended so the ECU can actively adjust the fueling based on fuel pressure changes or perform engine protection strategies if the fuel pressure deviates from the expected range.

Oil pressure sensor

The Rebel LS main terminated harness plugs directly into the factory oil pressure sensor using the early style 3-pin connector shown below. If you are using a later model Gen IV type of oil pressure sensor, a HT-186510 Oil pressure adapter harness can be used.

Wideband Oxygen sensor (WBO2)

The Nexus Rebel LS kits come equipped with a Bosch LSU 4.9 wideband oxygen sensor, which needs to be installed to read the exhaust gases exiting the engine. Utilizing this wideband lambda sensor enables the ECU to implement functions like closed-loop fuel control (O2 control), actively targeting desired fuel mixtures for any RPM and engine load combination. It also allows for engine protection strategies, limiting the engine if it detects that the fuel mixtures are running too lean.

Sensor Installation Notes:

1. Professional Installation: Installing the sensor in the exhaust requires a professional to weld the included sensor bung onto the exhaust pipe. Remember to disconnect the battery before performing any welding on the car.
   
2. Wiring Safety: Ensure that the sensor wiring does not come into contact with any exhaust piping to avoid damaging the wiring. 
3. Sensor Placement: The sensor should be installed in the exhaust pipe where it can read the average exhaust output from the engine, typically after the exhaust pipe collector.
   
4. Consideration for Catalytic Converters or Air Injection: If your exhaust system includes catalytic converters or air injection, install the sensor so it reads the exhaust stream before these components. Placement after these devices can lead to false readings and disrupt the closed-loop fuel control (O2 control).
   
5. Avoid condensation and sensor damage: Install the sensor on the upper half of the exhaust pipe at an angle to prevent exhaust condensation from contaminating the sensor.

Alternator

This Rebel LS main terminated harness is equipped with a DTM-2 plug to provide switched +12V power to alternators with built-in regulators. Additionally, the Rebel LS kit includes alternator adapter harnesses suitable for typical LS engine alternators with 2-pin Bosch or Yazaki connectors, as well as those with 4-pin Delco connectors:

• HT-186123 LS 2-pin Bosch alternator adapter

• HT-186124 LS 4-pin Delco alternator adapter

• HT-186125 LS 2-pin Yazaki alternator adapter

Using the adapter harnesses above excites the alternator using a 470-ohm inline resistor, serving as a replacement for the charge indicator light.

Coolant temperature sensor

Connect the coolant temperature connector to the 2-pin temperature sensor located on the left-hand side cylinder head as shown below.

Air temperature sensor

The air temperature sensor connector on the main harness plugs directly into the air temperature sensor included in the kit (HT-010200). The use of this sensor is recommended especially when not using the factory air intake box or the Mass Air Flow (MAF) sensor, where the factory air temp sensor is typically located.

The air temperature sensor should be installed at a location that best represents the actual intake air temperature entering the engine, which is typically on the intake pipe just before the throttle body.

Note: The Rebel LS ECU is preset to use the calibration for the included air temperature sensor by default, eliminating the need for any additional software setup for this sensor.

Knock sensors (Odd and Even banks)

The Rebel LS terminated harness uses Gen IV style knock sensor connectors, which plug into each sensor located on opposite sides of the engine. Utilizing knock sensors allows the Nexus Rebel LS ECU to be configured to detect knock and implement knock control strategies.

If you have the earlier style knock sensors located in the valley of the engine, a HT-186508 Gen III knock sensor adapter harness can be used. 

Spare Inputs and Outputs connector

This harness offers in-cabin breakout connectors populated with spare inputs and outputs available on the Nexus Rebel LS ECU. These spare inputs and outputs can be wired to additional sensors, switches, or used to control relays, solenoids, or warning lights.

1. Digital Pulsed Outputs (DPO)
   

Number of user definable channels: 5

Digital Pulsed Outputs (DPOs) are capable of generating pulsed waveforms with varying duty cycles, varying frequencies, or switched states (On or Off). When activated by the ECU, a DPO output  switches to ground. DPOs can be used to control various low-current devices (up to 3A max), such as boost control solenoids, shift lights, or tachometers. Additionally, DPOs can be used to switch relays to drive other high-current devices. 

1. Analog Voltage Inputs (AVI)
   

Number of user definable channels: 2

Analog Voltage Inputs (AVIs) are inputs that accept variable voltage signals ranging from 0-5V, typical of pressure, temperature, and position sensors. These inputs can also accommodate switches that alternate between two distinct voltage levels. AVIs feature a software-selectable 1K-ohm pull-up resistor to 5V, which is typically enabled for temperature-related sensors and switched to ground inputs. They are usually disabled for sensors with an external +5V supply, such as trim switches or linear position sensors.

1. Synchronized Pulsed Inputs (SPI)
   

Number of user definable channels: 4

Synchronized Pulsed Inputs are capable of measuring the duty cycle or frequency of a signal, in addition to analog voltages like AVIs. These inputs are suitable for various sensors, including flex fuel composition sensors or wheel speed sensors with a software-selectable 1K-ohm pull-up resistor to 5V, if the sensor requires. SPIs are compatible with both digital (hall effect or optical) and analog (reluctor) sensors. They have a maximum input voltage rating of 25V and can measure frequencies up to a maximum of 22.5kHz.

Haltech CAN

The Nexus Rebel LS ECU features a CAN channel that facilitates communication with a range of Haltech CAN expansion devices, available for separate purchase. This integration capability enhances the functionality and versatility of the ECU, allowing for a more comprehensive and customized vehicle control system. The range of compatible Haltech CAN expansion devices includes display dashes, keypads, power distribution modules, external wideband controllers, I/O expanders, thermocouple amplifiers, and CAN hubs.

Click for more information about Haltech CAN.

Transmission connector

The breakout connector for a transmission sub-harness can be utilized for transmission related functionality. The Rebel LS kits include a T56 manual transmission adapter harness to connect to the vehicle speed sensor. 

Note: Automatic transmission control is currently not supported, but we plan to expand the range to include some control packages for popular automatic transmissions in 2024.

Nexus Software Programmer (NSP)

Installing NSP

Haltech NSP  is the software used for tuning and programming the Nexus Rebel LS ECU. Follow these steps to install the Haltech NSP software:

1. Download the NSP installer - Go to the Haltech website Downloads section, and click on the download link for the NSP software.

2. Run the installer file - Once the download is complete, locate the downloaded file (usually in the ‘Downloads’ folder of your computer) and double-click on the file to run the Nexus Software Setup Wizard.

3. Launch Haltech NSP - Once the installation is complete, you can launch the Haltech NSP software from the Windows ‘Start’ menu or using the desktop shortcut that was created.

Going online with the ECU

With the NSP software open, connect the supplied Haltech USB cable between your laptop and the USB-C port on the front of the Nexus Rebel LS ECU.

The USB connection will let the NSP software automatically recognize the ECU and activate the unit in low power mode. This allows you to either upload a basemap or create a new one through the setup wizard before installing the ECU into the vehicle. In low power mode, the ECU’s inputs and outputs are disabled, ensuring you to safely configure your vehicle setup prior to installing the unit and powering it up.

Rebel LS ECU setup wizard

The NSP software provides you with a 7-step setup wizard to conveniently tailor the Rebel LS ECU settings to your specific LS application.

1. Name your vehicle - The first step requires you to assign a name to your vehicle, which essentially creates a folder on your laptop. NSP will use this folder to save maps or datalog files. You also have the option to add a brief description of the vehicle, giving you an overview of what’s set up in the map. This can be helpful if you save multiple versions of your map and want to quickly differentiate between files when opening them.

2. Base engine - The next step is where the actual setup begins, and you are given a list of GM LS engines to choose from as your base engine. This step defines the engine capacity and compression ratio in the map and provides additional information specific to the engine.

3. Camshafts - In Step 3, you can define the camshaft profile you are using in your engine. This sets parameters in your map related to fueling, spark, idle control, and O2 control to suit the type of camshaft you have.

4. Air intake system - This step allows you to define your air intake setup, whether the engine is naturally aspirated or uses forced induction. It also enables you to choose between a conventional cable-operated throttle and an electronic throttle and pedal system, commonly known as Drive-By-Wire (DBW). Based on your selection, the NSP software then allocates the necessary inputs and outputs for your specific air intake setup.

5. MAP sensor - Step 5 involves setting which MAP sensor you will use. The Nexus Rebel LS ECU comes equipped with an onboard 4-bar MAP sensor suitable for naturally aspirated and boosted engines up to 43 psi. Alternatively, an external MAP sensor can be used, with sensor calibration easily set by selecting a specific sensor from the list.

6. Fuel system - Here, you need to define the type of fuel being used and the specific fuel injectors on the engine. This step also allows you to choose between a manifold-referenced or constant pressure fuel regulator setup. You will also need to set the base fuel pressure. With this information, the Rebel LS ECU can automatically calculate the necessary injector pulse width to start and run the engine, allowing you to proceed directly to tuning.

7. Ignition system - This final step configures the Rebel LS ECU with the correct settings for your ignition coils by allowing you to select the appropriate type from a provided list.

Upon completion of the setup wizard, NSP will present a summary list of all the settings you’ve selected for confirmation. If any corrections are needed, you can easily go back through the steps and update them accordingly.

At this point, the Nexus Rebel ECU, in conjunction with a Rebel LS terminated harness, will be ready to start and run the engine with a base tune.

Engine start up guide

Starting your GM LS engine with a Nexus Rebel LS ECU and terminated harness involves several steps. Please note that this is a general overview, and the exact procedure may vary based on your specific application. Here are the basic steps:

1. Preparation - Ensure that the Rebel LS ECU is properly installed and securely mounted in your vehicle. Confirm all necessary wiring connections are made as per the Nexus Rebel LS terminated harness documentation and your engine’s specific requirements. 

Ensure the engine oil is at the correct level and of the right specification. Fill the cooling system with coolant and check for leaks. Check all belts for proper tension and condition. Ensure hoses are securely attached and free of cracks or wear.

2. Power and Ground - Use a sufficiently charged car battery, connected to the Rebel LS ECU as outlined in this quick start guide. The Rebel LS terminated harness does not provide grounding for your engine. Ensure your engine is properly grounded with a grounding strap connecting it to the battery.

3. Sensors and Inputs - Check that all required sensors (e.g., crank and cam sensors, MAP sensor, coolant and air temperature sensors, throttle position sensor, etc.) are correctly connected to the harness and that sensor values read accurately in the NSP software.

4. Outputs - Make correct connections for required outputs to engine components such as injectors, ignition coils, thermofan, and fuel pump.

5. Configure the Nexus Rebel LS ECU settings - Use the setup wizard in the NSP software to configure ECU settings, specifying engine type, injector size, ignition settings, and other parameters specific to your setup.

6. Safety Checks - Double-check all connections for issues like wiring shorts or loose connections that could pose a hazard. Verify that fuel pressure is within the expected range and there are no fuel leaks. Power cycle the ECU to prime the fuel pump and pressurize the fuel system.

7. Pre Start up - Briefly crank the engine to ensure it turns over smoothly and without any unusual sounds or issues. Once confident in the setup, start the engine using the ignition key or start button.

8. Monitor and Adjust - After the engine starts and idles, monitor data such as coolant temperature and wideband O2, and listen for any abnormal sounds. While the Nexus Rebel LS ECU will run the engine using a pre-configured base map, further tuning is needed for optimal performance, fuel economy, and emissions. Conduct thorough testing under various conditions.

Remember that engine tuning and setup can be complex and require expertise. If you are not experienced with EFI (Electronic Fuel Injection) systems and engine management, seeking assistance from a professional tuner is recommended for safe and reliable engine operation.

Specifications and references

Rebel LS ECU pinout

PIN	FUNCTION	COLOR		PIN	FUNCTION	COLOR		PIN	FUNCTION	COLOR
A1	Injector 1	Blue		C1	Crank	Yellow		E1	AX25+ (Auxiliary 25A)	Red / Blue
A2	Injector 2	Blue / Black		C2	Unused	Unused		E2	Fuel pump	Red / Yellow
A3	Injector 3	Blue / Brown		C3	Cam	Yellow		E3	Fan	Red / Orange
A4	Injector 4	Blue / Red		C4	Unused	Unused		E4	Injector / Ignition supply	Red / Green
A5	Injector 5	Blue / Orange		C5	Inputs / SPI 1	Gray / Brown
A6	Injector 6	Blue / Yellow		C6	Inputs / SPI 2	Gray / Red
A7	Injector 7	Blue / Green		C7	Inputs / SPI 3	Gray / Orange
A8	Injector 8	Blue / Violet		C8	Inputs / SPI 4	Gray / Yellow
A9	Outputs / DPO 1	Voilet / Black		C9	Crank / Cam supply	Orange / White
A10	Power ground output	Black		C10	Inputs / AVI 1	White
A11	Power ground output	Black		C11	Inputs / AVI 2	White / Yellow
A12	Outputs / DPO 2	Voilet / Brown		C12	Fuel pressure	White / Gray
A13	Ignition switch input	Pink		C13	Oil pressure	White / Violet
A14	Outputs / DPO 3	Violet / Red		C14	MAP	White / Green
A15	Outputs / DPO 4	Violet / Orange		C15	Throttle TPS 1	White / Orange
A16	Outputs / DPO 5	Violet / Yellow		C16	Throttle TPS 2	White / Black
A17	Tacho output	Voilet / Green		C17	APP 1	White / Brown
A18	Transmission supply	Pink / Red		C18	APP 2	White / Red
A19	Throttle / IAC 1	Brown / Black		C19	Transmission	Gray / Pink
A20	Throttle / IAC 2	Brown / Red		C20	Transmission / VSS	Gray / Light Green
A21	Throttle / IAC 3	Brown / Green		C21	Unused	Unused
A22	Throttle / IAC 4	Brown / Pink		C22	Unused	Unused
A23	CAN High	White		C23	Knock odd	Black / Blue
A24	CAN Low	Blue		C24	Knock even	Black / Green
A25	CAN supply	Pink / Brown		C25	+5V sensor supply	Orange
A26	Unused	Unused		C26	Sensor ground	Black / White
A27	Ignition 1	Yellow / Black		C27	Coolant temperature	Light Green
A28	Ignition 2	Yellow / Red		C28	Air temperature	Light Green / Black
A29	Ignition 3	Yellow / Orange		C29	WBI 1 Heater +	Gray
A30	Ignition 4	Yellow / Green		C30	WBI 1 Input	Yellow
A31	Ignition 5	Yellow / Brown		C31	WBI 1 Pump	Red
A32	Ignition 6	Yellow / Blue		C32	WBI 1 Nernst	Black
A33	Ignition 7	Yellow / Violet		C33	WBI 1 Heater -	White
A34	Ignition 8	Yellow / Gray		C34	WBI 1 Cal	Green

Rebel LS main terminated harness breakout connectors pinout

The information below details the pinout for the various breakout connectors on the main terminated harness. The images of the connectors display the wire side view, unless stated otherwise.

1. Fuel Injector breakout connector
   

1. Ignition coil breakout connector (Odd and Even banks)
   

1. Accelerator Pedal Position (APP) breakout connector
   

1. Throttle breakout connector
   

1. Spare Outputs breakout connector
   

1. Spare Inputs breakout connector
   

1. Transmission breakout connector
   

Rebel LS ECU parts overview

Rebel LS ECU LED Behavior

Rebel LS ECU specifications

Rebel LS ECU dimensions

GM LS1 (Gen III) engine

Click for more information about this engine.

GM LS2-LS3 (Gen IV) engine

Click for more information about this engine.

Further help and support

For any further questions or technical support regarding this product, please contact Haltech using the details found here.