Nexus Plug-in ECU - Honda EP3 and DC5
Congratulations on your purchase of a Nexus Honda EP3 / Honda DC5 Plug-in ECU. This vehicle-specific product allows you to seamlessly integrate a Nexus ECU into your vehicle without the complexity of wiring. With this hassle-free solution, you can start tuning right away.
Nexus ECUs are at the forefront of engine management systems, featuring cutting-edge technology and innovative features. Designed for the next generation of automotive enthusiasts and professionals, this state-of-the-art ECU combines powerful engine control with a range of additional functionalities, making it a versatile and comprehensive solution for everything from everyday driving to high-performance racing. With full compatibility across a wide range of Haltech devices, it simplifies engine configuration and additional functionalities, all programmable through a single software platform.
Supported Models
Nexus Plug-in ECU - Honda EP3
- Honda Civic EP3 (01-05)
- Honda Integra / Acura RSX DC5 (02-04)
- Manual transmissions only
Nexus Plug-in ECU - Honda DC5
- Honda Integra / Acura RSX DC5 (05-06)
- Manual transmissions only
What’s in the box?
- Nexus Honda Plug-in ECU
- Air temperature + wideband expansion harness 2.5m (8')
- Air temperature sensor (1/8 NPT)
- Aluminum weld on fitting 1/8 NPT -27 TPI for air temp sensor
- Mounting brackets and hardware
- Honda EP3 ECU - 3 x brackets (HT-039408, HT-039409, HT-039410)
- Honda DC5 ECU - 2 x brackets (HT-039409, HT-039410)
- 2.5m vacuum hose and T-piece
- Haltech USB-C cable
- Quick start guide
Optional Accessories (sold separately)
- HT-189002 - IO Expansion Harness 2.5m (8’)
- HT-010746 - LSU4.9 Wideband Hardware Pack
- HT-189003 - DBW Expansion Harness 2.5m (8’)
Nexus Plug-in ECU Overview and LED behaviour
Nexus Plug-in ECU Specs
Nexus Software Programmer
Installing the NSP Software
Haltech NSP is the software used for tuning and programming Nexus Plug-in ECUs. 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 Plug-in 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.
Setting up Wi-Fi communications
Wi-Fi communication is another method for connecting the Nexus Plug-in ECU to your laptop, serving as an alternative to a USB connection once the Wi-Fi module is enabled.
To set up your Wi-Fi connection follow these steps:
1. Open NSP and connect your Nexus Plug-in ECU using the provided USB-C cable.
2. Click on ‘Connections’ in the navigation tree and enable the Wi-Fi module.
3. Under ‘Connections’, select ‘Wi-Fi’ to set up your SSID and password. Note that your SSID must be at least 1 character long, and your password at least 8 characters.
4. Click ‘Apply’.
5. Power up the ECU using main power (ignition switch on), then go to your computer’s Network settings. Connect to your Nexus Plug-in ECU by selecting your chosen SSID and entering your password.
NOTE: The Wi-Fi antenna is internal on the Nexus Plug-in ECU. The unit must be powered by the main power source for Wi-Fi communication. Up to two computers can connect to the ECU via Wi-Fi, and one via USB-C, at any given time. When the Wi-Fi module is disabled, it is completely inactive and held in an OFF state.
Haltech Connect App
The Haltech Connect App enables you to connect wirelessly to and interact with your Haltech Nexus Plug-in ECU via your smartphone or tablet. View real-time data from the ECU, set up basic gauges, clear DTCs, assign wiring, and adjust select parameters. Available for free on Google Play (Android) and the Apple App Store (iOS).
Nexus Plug-in Setup Wizard
The NSP software, when used with a Nexus Plug-in ECU, features a comprehensive setup wizard designed to create a basemap tailored for your specific application. The process begins with naming your vehicle, which creates a dedicated folder on your laptop for saving maps and datalog files. You also have the option to add a vehicle description—a useful feature for quickly identifying different map versions.
Next, select your vehicle and engine type from the list of models supported by the ECU. Then, configure application-specific options such as fuel injectors and ignition systems.
The following steps involve selecting the auxiliary harness you’re using, which allows the ECU to assign I/Os to specific sensors, including a wideband O2 sensor, pressure sensors, a flex-fuel sensor, and more.
After completing these steps, NSP presents a summary of your selections for confirmation, allowing any necessary adjustments before finalizing the setup. This thorough process ensures that the Nexus Plug-in ECU is optimally configured to start and run the engine with your own base tune.
Application Specific Notes
This Nexus Plug-in ECU is compatible with the following vehicles:
Nexus Plug-in ECU - Honda EP3
- Honda Civic EP3 (01-05)
- Honda Integra / Acura RSX DC5 (02-04)
- Manual transmissions only
Nexus Plug-in ECU - Honda DC5
- Honda Integra / Acura RSX DC5 (05-06)
- Manual transmissions only
NOTE: The ECU will also support a K24A engine swap, provided the original vehicle engine harness is used to ensure correct ECU pinout assignments.
1. Wizard setup - Ensure that the ECU is correctly set up using the NSP software setup wizard before powering the unit through the vehicle.
Please note that the setup wizard serves only as a starting point, and the ECU will require appropriate tuning. Haltech is not responsible for any engine damage resulting from the improper use of base maps.
2. Air Temperature Sensor - The factory air temperature sensor can be used, or replaced with the one included in the kit.
3. Forced Induction - This Nexus Plug-in ECU supports engine modifications to accommodate forced induction (e.g. boost control) using the available outputs in the auxiliary connector.
4. Wideband O2 - The factory wideband O2 sensor (4-wire) is not supported. Instead, a Bosch LSU 4.9 or NTK sensor must be used via the auxiliary port connector.
5. MAP Sensor - The factory Manifold Absolute Pressure (MAP) sensor can be used or replaced with the ECU’s onboard 4‑bar MAP sensor for boosted applications. The ECU’s onboard MAP sensor barb must be physically connected to a vacuum port on the intake manifold using the included vacuum hose for the sensor to read vacuum and boost.
6. Flex Fuel System - The Nexus Plug-in ECU directly supports adding a flex fuel sensor by wiring it to one of the SPIs on the auxiliary connector. A flex fuel sensor allows the ECU to adjust the tune based on the ethanol percentage in the fuel system.
7. Multiplex Control Unit - This Nexus Plug‑in ECU supports the OEM Multiplex Control Unit communication signals used by the vehicle, enabling the ECU to control the coolant temperature display and battery warning light on the dash, as well as communicate with the climate control system for an A/C request signal.
8. Immobilizer system - This Nexus Plug-in ECU bypasses the factory immobilizer system regardless of status, and will automatically clear the immobilizer dash light on startup.
ECU Pinout Information Honda Civic EP3 (01-05) | Honda Integra / Acura RSX DC5 (02-04)
ECU Pinout Information Honda Integra / Acura RSX DC5 (05-06)
Auxiliary Connector
Nexus Plug-in ECUs are fitted with a 26-pin auxiliary connector that can be used to wire in sensors or devices not available in the vehicle from the factory. The ECU also includes an expansion harness that plugs into the auxiliary connector and can be conveniently routed within the engine bay. The included expansion harness (HT-189000) provides a connector for a Haltech air temperature sensor, which can be used in place of the factory sensor—integrated into the air flow meter. A wideband O2 sensor plug is also included and is controlled directly by the ECU’s onboard wideband O2 controller, allowing direct connection to a wideband hardware pack. A set of spare pins is also provided for the 26-pin connector, enabling the addition of sensors such as fuel and oil pressure sensors, flex fuel sensors, or custom DPO functions (e.g. boost control) that can be configured in the NSP software.
Pinout information for these connections is provided on the next page. To place pins into the auxiliary connector:
- Push bottom tabs to unlock
- Insert pin into harness side of connector
- Push top tabs to lock
NOTE: The switched 12V pins on the onboard CAN and auxiliary connectors can supply a total of 8A, shared across the three pins.
IO and DBW Expansion Harnesses
In addition to the basic expansion harness included, Haltech offers optional expansion harnesses (sold separately) to conveniently support common sensor upgrades for your Nexus Plug-in ECU:
HT-189002 - IO Expansion Harness 2.5m (8’)
This expansion harness adds connections for sensors such as a wideband O2 sensor, flex fuel composition sensor, oil pressure sensor, fuel pressure sensor, and air temperature sensor. It also includes spare pins for connecting to additional outputs available on the 26-pin connector.
HT-189003 - DBW Expansion Harness 2.5m (8’)
This expansion harness adds connections for sensors such as a wideband O2 sensor, flex fuel composition sensor, oil pressure sensor, fuel pressure sensor, air temperature sensor, a Bosch DBW throttle plug, and a universal plug for an Accelerator Pedal Position (APP) sensor. This connector can be used to wire an APP sensor of your choice, and the pinout information for the opposing connector is shown on the right.
Similar to the IO Expansion Harness, it also includes spare pins for connecting to additional outputs available on the 26-pin connector.
Nexus Plug-In ECU Installation
Honda EP3 Installation
The Nexus Honda EP3 Plug-in ECU replaces the factory unit, which is located behind the glove box. To access this location, the glove box must be removed. The included brackets allow the Nexus Honda EP3 Plug-in ECU to be installed using the factory bracket bolts and bolt locations. The glove box may be reinstalled after the installation is complete and the ECU has been configured using the NSP Setup Wizard.
Honda 02-04 DC5 ECU Installation
The Nexus Honda EP3 Plug-in ECU also supports the 02-04 DC5 Integra/RSX. The Nexus ECU replaces the factory unit, which is located under the glove box near the blower motor. To access this location, the underdash cover must be removed. The included brackets allow the Nexus ECU to be installed using the factory bracket bolts and bolt locations. The underdash cover may be reinstalled after the installation is complete and the ECU has been configured using the NSP Setup Wizard.
Honda 05-06 DC5 ECU Installation
The Nexus Honda DC5 Plug-in ECU replaces the factory unit, which is located under the glove box near the blower motor. To access this location, the underdash cover must be removed. The included brackets allow the Nexus Honda DC5 Plug-in ECU to be installed using the factory bracket bolts and bolt locations. The underdash cover may be reinstalled after the installation is complete and the ECU has been configured using the NSP Setup Wizard.
Haltech CAN System
The Nexus Plug-in ECU is equipped with an onboard CAN connector for direct connection to a wide range of Haltech CAN expansion products.
NOTE: The switched 12V pins on the onboard CAN and auxiliary connectors can supply a total of 8A, shared across the three pins.
Multiple CAN devices can be used simultaneously by linking them together using Haltech CAN cables and a Haltech CAN hub. Examples of Haltech CAN devices include the Haltech uC-10 display dash and the Haltech CAN keypad. The dash allows user-selected ECU or engine parameters to be displayed on a customizable screen, while the keypad enables you to scroll through multiple screens or control other functions managed by the ECU.
Additionally, a Nexus IO16 can be added to expand input and output functionality via the Haltech CAN system, supplementing the onboard capabilities of the ECU.
The diagram on the right illustrates an example of how to connect these Haltech CAN devices (sold separately).
NOTE: The switched 12V pins on the onboard CAN and auxiliary connectors can supply a total of 8A, shared across the three pins.
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