Nexus R3 Terminated Harness for Nissan RB

Nexus R3 Terminated Harness for Nissan RB

Nexus R3 Terminated Harness for Nissan RB




Overview

Congratulations on purchasing a Nissan RB terminated wiring harness for a Nexus R3 VCU! This specialized harness is designed for engine conversions using the following Nissan RB engines:

  1. RB20DET
  2. RB25DET
  3. RB25DET Neo
  4. RB26DETT
  5. RB30E

When used with a Nexus R3 VCU, your Nissan RB engine will have access to a wide range of performance and tuning capabilities. This Quick Start Guide will walk you through the installation of the terminated harness, as well as the available sub-harnesses and other compatible devices.

Harness Features

  1. Direct plug-in to Nexus R3 VCU
  2. Terminated engine bay and in-cabin connections
  3. CAN connectivity for Haltech CAN devices (e.g., dash displays, keypads, etc.)
  4. Sensor connections (e.g., CAS, temperature, fluid pressure, position, speed, etc.)
  5. Direct wideband lambda sensor connection
  6. Dual knock sensor support (Bosch sensors)
  7. Injector sub-harness options (EV1, EV6, Denso)
  8. Ignition sub-harness options (Direct fire ignition using R35 ignition coils)
  9. Direct VCU control for thermofan, fuel pump, and starter
  10. Compatible with cable throttle and DBW systems (cable throttle sub-harness included)
  11. Alternator control connection options
  12. Transmission wiring breakout connector
  13. Spare inputs and outputs located in both the cabin and the engine bay.

General Installation Warning

A Nexus series ECU or VCU allows connection to your laptop via the Nexus Software Programmer (NSP) using the included 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 this harness. Turning on the control unit with incorrect configurations can lead to damage to both the engine and control unit components.

This 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.

Avoid creating sparks or using electrical devices near flammable substances. Always disconnect the battery cables when working on the electrical systems of your vehicle. Make sure all fuel system components and wiring are installed away from heat sources, properly shielded if necessary, and in well-ventilated areas.

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.

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.



What’s in the bag?


  1. Nexus Nissan RB terminated harness (HT-186401)
  2. Nexus RB CAS adaptor to suit RB25 RB26 (HT-186142)
  3. Nexus RB CAS adaptor to suit RB30 (HT-186141)
  4. Nexus RB cable throttle sub-harness to suit RB25 RB26 (HT-186164)
  5. Nexus RB cable throttle sub-harness to suit RB30 (HT-186167)
  6. Nexus 2 Pin Yazaki alternator adaptor (HT-186125)
  7. Nexus 2 Pin EV1 alternator adaptor (HT-186126)
  8. Cabin adaptor harness (HT-186130)
  9. Opposing connectors and pins to use with boost control solenoid, spare inputs and outputs, and transmission breakout.

Available adaptors and sub-harnesses (sold separately)

  1. HT-186010 - i6 Sumitomo (Denso) primary injector harness
  2. HT-186004 - i6 Timer (EV1) primary injector harness
  3. HT-186007 - i6 GT150 (USCAR EV6) primary injector harness
  4. HT-186063 - i6 R35 COP ignition harness
  5. HT-186162 - Nexus DBW harness - suits Bosch

Harness Pinout Diagram




Harness Connections

Ignition Switch Input




The ignition switch input (pink) wire must be connected to a switched +12V source to turn the Nexus R3 VCU 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 VCU to momentarily turn off. The pink ignition switch input wire comes out of the connector for spare cabin inputs and outputs, where the APP adaptor is also integrated.

Nexus R3 VCU Battery Connection



For correct operation, the battery positive and battery negative must be connected to the Nexus R3 VCU at all times.

The Nexus R3 VCU’s positive (red) terminal must be connected to the positive (+) terminal of the battery. It is recommended to use a 150A fuse (sample CF fuse shown below) in this connection. Use the supplied red Surlok connector, along with a red 4 AWG battery cable (sold separately), to complete the connection.

The Nexus R3 VCU’s negative (black) terminal must be connected to the negative (–) terminal of the battery using the supplied black Surlok connector, along with a black 4 AWG battery cable to complete the connection.

Starter Motor Control


The Nissan RB terminated harness features a high-current output wire that can supply +12V (25A) to the starter solenoid when needed to engage the starter motor. This wire is terminated with a spade terminal that connects directly into the starter solenoid. The output is controlled by the VCU via the HCO 25A 1 pin, which is assigned to the starter control function in the VCU settings. Controlling the starter also requires a starter switch signal to be connected to the VCU. A white wire is fitted to the cabin connector and is pinned to AVI 1 (pin 8) for this purpose. This wire must be connected to the starter switch signal from the ignition key switch. Alternatively, the starter switch signal can be assigned to any available AVI/SPI within NSP, or toa CAN keypad button if your setup includes one.


Alternator

This harness is equipped with a 2 pin DTM plug to provide switched +12V power to alternators with built-in regulators. Additionally, the harness kit includes alternator adapter harnesses to suit the most common RB engine alternators, with the following connectors:

  1. HT-186126: Nexus 2 Pin EV1 Alternator Harness
  2. HT-186125: Nexus 2 Pin Yazaki Alternator Harness




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

Cam Angle Sensor (CAS)





The RB engines found in the Nissan Skyline R32,  R33, and R34 use an optical Cam Angle Sensor (CAS) located at the front of the exhaust cam. This single CAS assembly provides both engine speed and engine position to the VCU, eliminating the need for a separate crank sensor. The Nissan RB terminated harness supports the different CAS pinouts across the R32, R33, and R34 models by using the HT‑186142 CAS harness, where the wires are terminated with pins but left unterminated at the included CAS connector. This allows the user to pin the connector to suit the correct application. Use the two tables above for pinout information for the R32/R33 versus the R34 Cam Angle Sensor.

NOTE: The RB optical Cam Angle Sensors are grounded to the engine through the CAS assembly. Do not connect the ground pin to any sensor ground, as this can cause inaccurate readings for other sensors.

Similarly, the RB30 engine uses an optical Cam Angle Sensor (CAS); however, the sensor is built into the distributor as a single assembly. The Nissan RB terminated harness supports the RB30 CAS through the use of the HT‑186141 RB30 CAS  adaptor, which plugs directly into the distributor.




Wideband Lambda Sensor


The Nissan RB terminated harness is equipped with a DTM‑6 connector that plugs into a Haltech wideband hardware pack and is directly controlled by the wideband controller built into the Nexus R3
VCU. Wideband hardware packs are available with either a Bosch LSU4.9 sensor (HT-010746) or NTK sensor (HT-010747). Using a wideband lambda sensor allows the VCU to utilise functions such as closed‑loop fuel control, where the VCU targets the desired fuel mixture for any RPM and engine load combination. It also enables the VCU to implement engine protection strategies when it detects that the fuel mixture is running too lean.

Knock Sensors


The Nissan RB terminated harness features two knock sensor connectors that plug into two Bosch knock sensors (sold separately). Bosch knock sensors detect a wider range of frequencies, making them more suitable for performance applications. Utilizing knock sensors allows the Nexus R3 VCU to detect knock and implement knock control strategies.

Fuel Injector Breakout




The Nexus Nissan RB terminated harness uses an injector breakout connector that plugs into multiple types of injector sub‑harnesses (sold separately). The choice of sub‑harness depends on the type of injector connectors being used. Each injector plug is labeled accordingly to easily identify which injector on the engine it connects to.

Flex Fuel Sensor


The Nexus Nissan RB terminated harness also features an optional connector that plugs into a Haltech Flex Fuel Sensor. Using a Flex Fuel Sensor enables the VCU to make real-time adjustments to optimize the tune for varying ethanol blends.

Ignition Coil Breakout






The Nexus Nissan RB terminated harness uses an ignition coil breakout connector that plugs into the HT‑186063 R35 Coil ignition sub‑harness (sold separately). This configuration eliminates the need for the factory external igniter module found on earlier RB engines, simplifying the wiring harness while upgrading the ignition system to use high‑output ignition coils. Alternatively, the breakout connector may also be used to wire the main harness to support a different ignition coil and igniter combination, if required.


Ignition Coil Ground



The Nexus Nissan RB terminated harness also includes an integrated grounding for the ignition coils, using a 10 mm ring terminal that must be bolted to the engine head.

NOTE: Make sure your engine is adequately grounded using a grounding cable or earthing strap that connects the engine to the battery. This ground ring terminal does not provide grounding for your engine.


Manifold Absolute Pressure (MAP) Sensor


Air Flow Meters (AFMs) or MAF sensors are not primarily used by the Nexus R3 VCU; instead, engine load is measured using a MAP sensor. The Nexus R3 VCU features an onboard 4‑bar MAP sensor capable of measuring up to 43 psi of boost pressure. This can be utilised by connecting a vacuum hose from the MAP sensor barb to a vacuum port on the intake manifold, or by using a T‑piece in line with the fuel pressure regulator’s vacuum hose. If the engine will be running more than 43 psi of boost, an external MAP sensor can be used and wired to the spare connector located at the engine‑bay end of the harness.

Oil and Fuel Pressure Sensors





This harness plugs directly into Haltech oil and fuel pressure sensors using the Delphi 3-pin pressure sensor connector shown below. While oil and fuel pressure sensors are not required for the engine to run, they are highly recommended to enable the VCU to make fueling adjustments and provide engine protection.

Coolant and Intake Air Temperature






The Nexus Nissan RB terminated harness is equipped with connectors that plug directly into the factory 2-pin coolant temperature sensor and a Haltech air temperature sensor (HT-010206). These are vital sensors that the VCU uses as part of the Volumetric Efficiency (VE) fuel model and are often used for engine protection as well.

Oil Pressure Gauge Signal


The Nexus Nissan RB terminated harness is fitted with a connector that plugs into the factory oil pressure gauge sensor that runs to pin 19 of the cabin connector input allowing connection to an analog gauge.

Coolant Temperature Gauge Signal


The Nexus Nissan RB terminated harness is fitted with a connector that plugs into the factory coolant temperature gauge sensor. This single pin sensor is not used by the VCU, but the wire runs from the sensor to pin 18 of the cabin connector input, allowing connection to an analog coolant temperature gauge.

Thermofan Control


This harness provides direct thermofan control using the Red/Orange 10AWG cable. Use this cable to supply +12V power directly to the thermofan and leverage VCU 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).

Fuel Pump Control





The harness also provides direct fuel pump control using the Red/Yellow 10AWG terminated cable. Use this cable to supply +12V power directly to the fuel pump, allowing the VCU to prime the pump when the system is turned on and to implement safety functions, such as automatically turning the pump off when the VCU no longer detects an RPM signal.



Throttle Breakout Connector



The Nexus Nissan RB terminated harness features a throttle breakout connector that provides the option to use either the included cable‑throttle sub‑harness or to upgrade to electronic throttle control using a Bosch DBW sub‑harness (sold separately).

Cable Throttle Sub-harness


There are two cable throttle sub‑harnesses included in the kit, each with connectors to suit the common types of idle valves (AAC), Fast Idle Control Devices (FICD), and Throttle Position Sensors (TPS) used on RB25, RB26, and RB30 engines.

HT-186164 - For twin cam engines, or engines that use the newer style connectors, the HT‑186164 cable throttle sub‑harness is typically used. Similarly, engines equipped with a single connector TPS must be tested to determine whether the sensor is only a switch. If it is, the TPS must be replaced with a variable type unit from another RB engine or an appropriate aftermarket alternative for the Haltech ECU or VCU to use. The TPS branch has also been provisioned with a flying lead connection to allow the end user additional pinout options for the Nissan throttle position sensor. Refer to the table below for pinout information.





HT‑186167 - This cable throttle sub‑harness is typically used with an RB30 equipped with the earlier style connectors. It is important to note that the TPS on these engines may either be a single connector switch type sensor or a dual connector sensor that provides both a switched signal and a variable signal. Haltech ECUs and VCUs require a variable type TPS; therefore, if the engine is equipped with a switch‑type TPS, it must be replaced with the dual‑connector type or an appropriate aftermarket variable TPS.





DBW Throttle Sub-harness


If you’re upgrading from the conventional cable‑throttle system to electronic throttle, also known as Drive‑By‑Wire (DBW), the DBW throttle sub‑harness (HT‑186162) can be used to plug into the throttle breakout connector and connect to a Bosch electronic throttle body.

Accelerator Pedal Position


To complete the DBW throttle system, a DBW pedal or Accelerator Pedal Position (APP) assembly must be used to replace the mechanical pedal from the cable throttle system. The supplied cabin input connector includes an integrated universal 6 pin DTM connector for this purpose, allowing you to wire in the pedal of your choice. The cabin connector also includes a dedicated pin (Pin 21) designed for connection to a brake pedal switch or brake light signal, as part of the DBW control strategy. This brake input signal is expected to read +12V whenever the brake pedal is pressed.

Boost Control

The Nexus Nissan RB terminated harness features a dedicated 2 pin DTM connector for wiring a Haltech boost control solenoid. A 3-port boost solenoid, such as the HT-020400, is suitable for performance applications and provides much more stable control over the desired boost pressure.

VCT


For engines equipped with VCT, the Nexus Nissan RB terminated harness includes a connector that plugs into the VCT solenoid, located behind the timing belt cover near the intake ports. This solenoid is tuned using the Cam Control function in the NSP software to maximise engine performance. If the engine is not equipped with VCT, this connector and the associated output on the Nexus R3 VCU can be repurposed for a different application.

Haltech CAN connection







This harness is equipped with 4 pin DTM connectors—one at the cabin end and the other at the engine bay end of the harness. These CAN connectors are designed to connect to Haltech CAN devices (e.g., display dash, keypad, PDM), which further expand the functionality of the application. If you are using multiple Haltech CAN devices, a Haltech CAN Hub can be used to increase the number of available connection ports.

Spare Inputs and Outputs


The Nissan RB terminated harness features two connectors with spare inputs and outputs that can be used to wire in additional sensors, switches, or to control relays, solenoids, warning lights, or other devices you want the VCU to control. The connector located at the cabin end of the harness is labelled “Cabin” and uses a 26-pin connector. The other connector, labelled “Spare,” is located at the engine bay end of the harness and uses a 12-pin DTM connector. Both opposing connectors are supplied in the kit, with pinout information provided below for reference.






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