The terms you'll meet most
| Term | Stands for | What it means in practice |
|---|---|---|
| AVI | Analogue Voltage Input | An input that reads a voltage anywhere between 0 and 5V. This is where sensors like throttle position, pressure and temperature connect |
| SPI | Synchronised Pulsed Input | An input that reads on/off pulses and measures their frequency or duty. It accepts digital or reluctor signals switching at 0V, 5V or 12V. Use it for speed sensors, flex fuel sensors and switches |
| DPO | Digital Pulsed Output | An output that switches on and off at a set frequency and duty, at 0V, 5V, 8V or 12V levels. It drives solenoids, relays and gauges |
| Crank (Trigger) | Trigger input | The main engine position signal, normally at least one pulse per cylinder firing event |
| Cam (Home) | Home input | The sync signal, normally at least one pulse per full engine cycle, so the ECU knows which stroke each cylinder is on |
| OBPS | On Board Pressure Sensor | The pressure sensor built into the ECU case, often used as the MAP sensor with a hose to the manifold |
| DBW | Drive By Wire | An electronic throttle, where the ECU moves the throttle blade with a motor based on the pedal sensor |
Why it matters when you wire
The first three terms are the ones that trip people up. A sensor with a smoothly changing voltage belongs on an AVI. A sensor that sends pulses, like a wheel speed sensor, needs an SPI, because an AVI isn't built to count fast pulses. Anything the ECU has to switch, such as a boost solenoid or fan relay, needs an output like a DPO. Put a device on the wrong type of pin and ESP either won't let you assign it or the reading will be meaningless.
The trigger and home inputs are the engine position inputs, so plan your crank and cam sensors onto them before you start handing out other pins.
For more on navigating ESP, see the keyboard reference, and the DTC index when a fault code appears.
