Auto Control Wiring

Solenoid Wiring

Much like running an ECU, there are many inputs and outputs you will need to wire for auto control

Often the solenoids in automatic transmissions are “High-Side” operated, that is, the control unit outputs VBatt on the output pins. Most ECU Aux Outputs typically run “Low-Side”, that is, they are supplying a path to ground, not a positive voltage.

While some pins on our ECU’s can supply high-side, these pins are typically designed for Stepper and H-brige (i.e. E-Throttle), and these pins may lack the amperage requirements or PWM control needed for transmission solenoids.

In some use instances, it may be great use case for a PDM to drive the transmission solenoids. PDM’s also allow you to offload IO onto the PDM, keeping more IO free on the ECU itself for running your engine.

Otherwise you can also use solid state relays to convert low-side ECU Aux. outputs to high-side. Just be sure to check the specs of your chosen relays, to ensure they have the required amperage ratings, and are able to switch at the frequency your transmission requires on it’s PWM solenoids if you plan to use them PWM.

Speed Sensors

All the transmissions we support measure output shaft speeds. This will typically be done using VR/Reluctor sensors. This will sometimes require you to run your own VR to Hall converters to send the signal to the ECU. Sending a VR signal directly to a normal Digital Input pin on an ECU or PDM can result in no signal at slow speeds. In testing, the Subaru rear output speed sensors wasn’t detectable until roughly 40kph, however the GM 4L60E was readable at very low speeds for example.

If you are having issues reading VR sensor signals at low speeds, there are many VR to Hall converters on the market you can use to convert to a hall signal for the ECU.

Selector Position

Most, but not all transmissions we support have a single wire per shift selector position, which is quite costly for IO.

There are provisions in PCLink to input gear detection as different voltages on a single AN Volt pin, saving you IO. This can be done using aftermarket converter boxes or custom hardware. If you are retaining the “PRNDL” lights on your dash, be mindful that they often use the same wiring that the ECU/TCU does for gear detection.