Legacy Hellen ECU Information
This page is for the legacy series of Miata Hellen ECU Boards
Using an External Wideband Controller
In the case you wish to use an external wideband controller such as an AEM X-Series Wideband UEGO AFR Sensor Controller Gauge, the wideband sensor should be plugged into the wideband controller instead of directly into the ECU. The best way to wire in the controller is directly to the old narrow band oxygen sensor plug on the car based off the diagram below. In this diagram, pin 1 goes to the controller analogue output, pin 2 to the signal ground, pin 3 to the controller 12V input and pin 4 to the other controller ground (if applicable). Make sure to double check the voltages on the pins before connecting the controller to them. The external controller also requires additional setup in Tuner Studio which will be covered later.
Additional Tuner Studio Steps for an External Wideband Controller
To set up the external wideband controller there are several additional steps in Tuner Studio. First, your display units should be set to AFR for this as already stated. If you forgot to do this earlier, press CTRL + P to open the vehicle properties. Now, open the Aux Sensors dialog under Sensors and the Full Pinout 3/3 dialog under Controllers. As per the diagram below, set the AFR ADC Input and ADC Input to the pin corresponding with O2S (pin 2C for the example). for the values in the Aux Linear Sensor #1 box you need to reference the manual of your wideband controller for what voltages correspond to its AFR outputs. In the example below, 0V corresponds to an AFR of 10.0 and 4.99V corresponds to an AFR of 19.98. Once these are set, click Burn.
